The city of Ōtautahi/Christchurch experienced a series of earthquakes that began on September 4th, 2010. The most damaging event occurred on February 22nd, 2011 but significant earthquakes also occurred on June 13th and December 23rd with aftershocks still occurring well into 2012. The resulting disaster is the second deadliest natural disaster in New Zealand’s history with 185 deaths. During 2011 the Canterbury earthquakes were one of the costliest disasters worldwide with an expected cost of up to $NZ30 billion.
Hundreds of commercial buildings and thousands of houses have been destroyed or are to be demolished and extensive repairs are needed for infrastructure to over 100,000 homes. As many as 8,900 people simply abandoned their homes and left the city in the first few months after the February event (Newell, 2012), and as many as 50,000 may leave during 2012. In particular, young whānau and single young women comprised a disproportionate number of these migrants, with evidence of a general movement to the North Island.
Te Puni Kōkiri sought a mix of quantitative and qualitative research to examine the social and economic impacts of the Christchurch earthquakes on Māori and their whānau. The result of this work will be a collection of evidence to inform policy to support and assist Māori and their whānau during the recovery/rebuild phases. To that end, this report triangulates available statistical and geographical information with qualitative data gathered over 2010 and 2011 by a series of interviews conducted with Māori who experienced the dramatic events associated with the earthquakes.
A Māori research team at Lincoln University was commissioned to undertake the research as they were already engaged in transdisciplinary research (began in the May 2010), that focused on quickly gathering data from a range of Māori who experienced the disaster, including relevant economic, environmental, social and cultural factors in the response and recovery of Māori to these events.
Participants for the qualitative research were drawn from Māori whānau who both stayed and left the city. Further data was available from ongoing projects and networks that the Lincoln research team was already involved in, including interviews with Māori first responders and managers operating in the CBD on the day of the February event. Some limited data is also available from younger members of affected whānau.
Māori in Ōtautahi/Christchurch City have exhibited their own culturally-attuned collective responses to the disaster. However, it is difficult to ascertain Māori demographic changes due to a lack of robust statistical frameworks but Māori outward migration from the city is estimated to range between 560 and 1,100 people.
The mobility displayed by Māori demonstrates an important but unquantified response by whānau to this disaster, with emigration to Australia presenting an attractive option for young Māori, an entrenched phenomenon that correlates to cyclical downturns and the long-term decline of the New Zealand economy. It is estimated that at least 315 Māori have emigrated from the Canterbury region to Australia post-quake, although the disaster itself may be only one of a series of events that has prompted such a decision.
Māori children made up more than one in four of the net loss of children aged 6 to 15 years enrolled in schools in Greater Christchurch over the year to June 2011. Research literature identifies depression affecting a small but significant number of children one to two years post-disaster and points to increasing clinical and organisational demands for Māori and other residents of the city.
For those residents in the eastern or coastal suburbs – home to many of the city’s Māori population - severe damage to housing, schools, shops, infrastructure, and streets has meant disruption to their lives, children’s schooling, employment, and community functioning. Ongoing abandonment of homes by many has meant a growing sense of unease and loss of security, exacerbated by arson, burglaries, increased drinking, a stalled local and national economy, and general confusion about the city’s future.
Māori cultural resilience has enabled a considerable network of people, institutions, and resources being available to Māori , most noticeably through marae and their integral roles of housing, as a coordinating hub, and their arguing for the wider affected communities of Christchurch.
Relevant disaster responses need to be discussed within whānau, kōhanga, kura, businesses, communities, and wider neighbourhoods. Comprehensive disaster management plans need to be drafted for all iwi in collaboration with central government, regional, and city or town councils.
Overall, Māori are remarkably philosophical about the effects of the disaster, with many proudly relishing their roles in what is clearly a historic event of great significance to the city and country. Most believe that ‘being Māori’ has helped cope with the disaster, although for some this draws on a collective history of poverty and marginalisation, features that contribute to the vulnerability of Māori to such events.
While the recovery and rebuild phases offer considerable options for Māori and iwi, with Ngāi Tahu set to play an important stakeholder in infrastructural, residential, and commercial developments, some risk and considerable unknowns are evident. Considerable numbers of Māori may migrate into the Canterbury region for employment in the rebuild, and trades training strategies have already been established.
With many iwi now increasingly investing in property, the risks from significant earthquakes are now more transparent, not least to insurers and the reinsurance sector. Iwi authorities need to be appraised of insurance issues and ensure sufficient coverage exists and investments and developments are undertaken with a clear understanding of the risks from natural hazards and exposure to future disasters.
New Zealand has experienced several strong earthquakes in its history. While an earthquake cannot be prevented from occurring, planning can reduce its consequences when it does occur. This dissertation research examines various aspects of disaster risk management policy in Aotearoa New Zealand.
Chapter 2 develops a method to rank and prioritise high-rise buildings for seismic retrofitting in Wellington, the earthquake-prone capital city of New Zealand. These buildings pose risks to Wellington’s long-term seismic resilience that are of clear concern to current and future policymakers. The prioritization strategy we propose, based on multi-criteria decision analysis (MCDA) methods, considers a variety of data on each building, including not only its structural characteristics, but also its location, its economic value to the city, and its social importance to the community around it. The study demonstrates how different measures, within four general criteria – life safety, geo-spatial location of the building, its economic role, and its socio-cultural role – can be operationalized into a viable framework for determining retrofitting/demolition policy priorities.
Chapter 3 and chapter 4 analyse the Residential Red Zone (RRR) program that was implemented in Christchurch after the 2011 earthquake. In the program, approximately 8,000 homeowners were told that their homes were no longer permittable, and they were bought by the government (through the Canterbury Earthquake Recovery Authority).
Chapter 3 examines the subjective wellbeing of the RRR residents (around 16000 people) after they were forced to move. We consider three indicators of subjective wellbeing: quality of life, stress, and emotional wellbeing. We found that demographic factors, health conditions, and the type of government compensation the residents accepted, were all significant determinants of the wellbeing of the Red Zone residents. More social relations, better financial circumstances, and the perception of better government communication were also all associated positively with a higher quality of life, less stress, and higher emotional wellbeing.
Chapter 4 concentrates on the impact of this managed retreat program on RRR residents’ income. We use individual-level comprehensive, administrative, panel data from Canterbury, and difference in difference evaluation method to explore the effects of displacement on Red Zone residential residents. We found that compared to non-relocated neighbours, the displaced people experience a significant initial decrease in their wages and salaries, and their total income. The impacts vary with time spent in the Red Zone and when they moved away. Wages and salaries of those who were red-zoned and moved in 2011 were reduced by 8%, and 5.4% for those who moved in 2012. Females faced greater decreases in wages and salaries, and total income, than males. There were no discernible impacts of the relocation on people’s self-employment income.
Brooklands Lagoon / Te Riu o Te Aika Kawa (‘Brooklands’) is an important wetland and estuarine ecosystem in Canterbury. It is a site of cultural significance to Ngāi Tūāhuriri, and is also valued by the wider community. Home to an array of life, it is connected to the Pūharakekenui/Styx and Waimakariri rivers, and is part of a wetland landscape complex that includes the Avon-Heathcote / Ihutai estuary to the south and the Ashley / Rakahuri estuary to the north. Notionally situated within the territorial boundary of Christchurch City Council and jurisdictionally encompassed by the regional council Environment Canterbury, it has been legally determined to be part of the coastal marine area. The complicated administrative arrangements for the lagoon mirror the biophysical and human challenges to this surprisingly young ecosystem since its formation in 1940.
Here we present a synthesis of the historical events and environmental influences that have shaped Brooklands Lagoon. Before existing as an intertidal ecosystem, the Waimakariri river mouth was situated in what is now the southern end of the lagoon. A summary timeline of key events is set out in the table below. These included the diversion of the Waimakariri River mouth via the construction of Wrights Cut in the 1930s, which influenced the way that the lower reaches of the river interacted with the land and sea. A large flood in 1940 shifted the river mouth ~2 to 3 kilometres north, that created the landscape that we see today. However, this has not remained stable, as the earthquake sequence in 2010 and 2011 subsided the bed of the estuary.
The changes are ongoing, as sea level rise and coastal inundation will place ongoing pressure on the aquatic ecosystem and surrounding land. How to provide accommodation space for Brooklands as an estuary will be a key planning and community challenge, as Environment Canterbury begins the engagement for the review of its Regional Coastal Plan. There is also a requirement to safeguard its ecological health under the 2020 National Policy Statement on Freshwater Management. This will necessitate an integrated mountains to sea (ki uta ki tai) management approach as the lagoon is affected by wider catchment activities. We hope that this report will contribute to, and inform these processes by providing a comprehensive historical synthesis, and by identifying considerations for the future collaborative management of Brooklands Lagoon, and protection of its values. In essence, we suggest that Te Riu o Te Aika Kawa deserves some sustained aroha.
Probabilistic Structural Fire Engineering (PSFE) has been introduced to overcome the limitations of current conventional approaches used for the design of fire-exposed structures. Current structural fire design investigates worst-case fire scenarios and include multiple thermal and structural analyses. PSFE permits buildings to be designed to a level of life safety or economic loss that may occur in future fire events with the help of a probabilistic approach. This thesis presents modifications to the adoption of a Performance-Based Earthquake Engineering (PBEE) framework in Probabilistic Structural Fire Engineering (PSFE). The probabilistic approach runs through a series of interrelationships between different variables, and successive convolution integrals of these interrelationships result in probabilities of different measures. The process starts with the definition of a fire severity measure (FSM), which best relates fire hazard intensity with structural response. It is identified by satisfying efficiency and sufficiency criteria as described by the PBEE framework. The relationship between a fire hazard and corresponding structural response is established by analysis methods. One method that has been used to quantify this relationship in PSFE is Incremental Fire Analysis (IFA). The existing IFA approach produces unrealistic fire scenarios, as fire profiles may be scaled to wide ranges of fire severity levels, which may not physically represent any real fires. Two new techniques are introduced in this thesis to limit extensive scaling. In order to obtain an annual rate of exceedance of fire hazard and structural response for an office building, an occurrence model and an attenuation model for office fires are generated for both Christchurch city and New Zealand. The results show that Christchurch city is 15% less likely to experience fires that have the potential to cause structural failures in comparison to all of New Zealand. In establishing better predictive relationships between fires and structural response, cumulative incident radiation (a fire hazard property) is found to be the most appropriate fire severity measure. This research brings together existing research on various sources of uncertainty in probabilistic structural fire engineering, such as elements affecting post-flashover fire development factors (fuel load, ventilation, surface lining and compartment geometry), fire models, analysis methods and structural reliability. Epistemic uncertainty and aleatory uncertainty are investigated in the thesis by examining the uncertainty associated with modelling and the factors that influence post-flashover development of fires. A survey of 12 buildings in Christchurch in combination with recent surveys in New Zealand produced new statistical data on post-flashover development factors in office buildings in New Zealand. The effects of these parameters on temperature-time profiles are evaluated. The effects of epistemic uncertainty due to fire models in the estimation of structural response is also calculated. Parametric fires are found to have large uncertainty in the prediction of post-flashover fires, while the BFD curves have large uncertainties in prediction of structural response. These uncertainties need to be incorporated into failure probability calculations. Uncertainty in structural modelling shows that the choices that are made during modelling have a large influence on realistic predictions of structural response.
High demolition rates were observed in New Zealand after the 2010-2011 Canterbury Earthquake Sequence despite the success of modern seismic design standards to achieve required performance objectives such as life safety and collapse prevention. Approximately 60% of the multi-storey reinforced concrete (RC) buildings in the Christchurch Central Business District were demolished after these earthquakes, even when only minor structural damage was present. Several factors influenced the decision of demolition instead of repair, one of them being the uncertainty of the seismic capacity of a damaged structure. To provide more insight into this topic, the investigation conducted in this thesis evaluated the residual capacity of moderately damaged RC walls and the effectiveness of repair techniques to restore the seismic performance of heavily damaged RC walls. The research outcome provided insights for developing guidelines for post-earthquake assessment of earthquake-damaged RC structures. The methodology used to conduct the investigation was through an experimental program divided into two phases. During the first phase, two walls were subjected to different types of pre-cyclic loading to represent the damaged condition from a prior earthquake, and a third wall represented a repair scenario with the damaged wall being repaired using epoxy injection and repair mortar after the pre-cyclic loading. Comparisons of these test walls to a control undamaged wall identified significant reductions in the stiffness of the damaged walls and a partial recovery in the wall stiffness achieved following epoxy injection. Visual damage that included distributed horizontal and diagonal cracks and spalling of the cover concrete did not affect the residual strength or displacement capacity of the walls. However, evidence of buckling of the longitudinal reinforcement during the pre-cyclic loading resulted in a slight reduction in strength recovery and a significant reduction in the displacement capacity of the damaged walls. Additional experimental programs from the literature were used to provide recommendations for modelling the response of moderately damaged RC walls and to identify a threshold that represented a potential reduction in the residual strength and displacement capacity of damaged RC walls in future earthquakes. The second phase of the experimental program conducted in this thesis addressed the replacement of concrete and reinforcing steel as repair techniques for heavily damaged RC walls. Two walls were repaired by replacing the damaged concrete and using welded connections to connect new reinforcing bars with existing bars. Different locations of the welded connections were investigated in the repaired walls to study the impact of these discontinuities at the critical section. No significant changes were observed in the stiffness, strength, and displacement capacity of the repaired walls compared to the benchmark undamaged wall. Differences in the local behaviour at the critical section were observed in one of the walls but did not impact the global response. The results of these two repaired walls were combined with other experimental programs found in the literature to assemble a database of repaired RC walls. Qualitative and quantitative analyses identified trends across various parameters, including wall types, damage before repair, and repair techniques implemented. The primary outcome of the database analysis was recommendations for concrete and reinforcing steel replacement to restore the strength and displacement capacity of heavily damaged RC walls.
4th September 2010 a 7.1 magnitude earthquake strikes near Christchurch, New Zealand’s second largest city of approximately 370,000 people. This is followed by a 6.3 magnitude quake on 22nd February 2011 and a 6.4 on 13th June. In February 181 people died and a state of national emergency was declared from 23 February to 30th April. Urban Search and Rescue teams with 150 personnel from New Zealand and 429 from overseas worked tirelessly in addition to Army, Police and Fire services. Within the central business district 1,000 buildings (of 4,000) are expected to be demolished. An estimated 10,000 houses require demolition and over 100,000 were damaged. Meanwhile the over 7,000 aftershocks have become part of the “new normal” for us all.
During this time how have libraries supported their staff? What changes have been made to services? What are the resourcing opportunities?
This presentation will provide a personal view from Lincoln University, Te Whare Wanaka o Aoraki, Library Teaching and Learning. Lincoln is New Zealand's third oldest university having been founded in 1878. Publicly owned and operated it is New Zealand's specialist land-based university. Lincoln is based on the Canterbury Plains, 22 kilometres south of Christchurch. On campus there was mostly minor damage to buildings while in the Library 200,000 volumes were thrown from the shelves. I will focus on the experiences of the Disaster Team and on our experiences with hosting temporarily displaced staff and students from the Christchurch Polytechnic Institute of Technology, Library, Learning & Information Services.
Experiences from two other institutions will be highlighted:
Christchurch City Libraries, Ngā Kete Wānanga-o-Ōtautahi. Focusing on the Māori Services Team and the Ngā Pounamu Māori and Ngāi Tahu collections. The Central library located within the red zone cordon has been closed since February, the Central library held the Ngā Pounamu Māori and Ngai Tahu collections, the largest Māori collections in the Christchurch public library network. The lack of access to these collections changed the way the Māori Services Team, part of the larger Programmes, Events and Learning Team at Christchurch City Libraries were able to provide services to their community resulting in new innovative outreach programmes and a focus on promotion of online resources. On 19th December the “temporary” new and smaller Central library Peterborough opened. The retrieved Ngā Pounamu Māori and Ngai Tahu collections "Ngā rakau teitei e iwa”, have since been re-housed and are once again available for use by the public.
Te Rūnanga o Ngāi Tahu. This organisation, established by the Te Rūnanga o Ngāi Tahu Act 1996, services the statutory rights for the people of Ngāi Tahu descent and ensures that the benefits of their Treaty Claim Settlement are enjoyed by Ngāi Tahu now and in the future. Ngāi Tahu are the indigenous Māori people of the southern islands of New Zealand - Te Waipounamu. The iwi (people) hold the rangatiratanga or tribal authority to over 80 per cent of the South Island. With their headquarters based in the central business they have also had to be relocated to temporary facilities. This included their library/archive collection of print resources, art works and taonga (cultural treasures).
Knowledge of past climate variability is essential for understanding present and future climate trends. This study used Halocarpus biformis (pink pine) ring-width chronologies to investigate palaeotemperature history in Westland, New Zealand. The ensuing reconstruction is among the longest palaeoseries produced for New Zealand to date. It is in good agreement with other tree-ring-based records, and with instrumental (both local and hemispheric) data.
Thirteen pink pine chronologies were developed. Ring-width measurements were detrended using the Regional Curve Standardisation method to retain as much low-frequency variance as possible. Crossdating revealed the existence of a strong common signal among trees. Inter-site comparison indicated that a common control mechanism affected tree growth not only within sites, but also across sites.
To determine whether climate was the main factor that controlled the growth of pink pine in Westland, correlation and response function analyses were employed. Temperature, precipitation and the Southern Oscillation Index were tested for their relationship with tree growth. Mean monthly temperature was identified as the primary growth-limiting factor. Chronologies were positively correlated with temperature over an extended period (5-17 months), and climate response modelling showed that temperature explained 11-60% variance in the tree-ring data. The highest and most stable correlations occurred between tree growth and summer (January-March) temperatures.
Tree-ring data from the six sites that contained the strongest temperature signal were combined, and the Westland Regional Chronology (WRC) was developed. The WRC was then used to reconstruct January-March temperatures back to A.D. 1480. The calibration model explained 43% of the variance in temperature, and all calibration and verification tests were passed at high levels of significance. The reconstruction showed that temperatures in Westland have been following a positive trend over the last 520 years. The coolest 25-year period was 1542-1566, while temperatures reached their maximum in 1966-1990. Spectral analysis of the Westland palaeotemperature record revealed cycles at periods of about 3, 5-6, 11, 14, 22, 45 and 125 years.
This study also confirmed that climate response is species-dependent. A separate exercise, which compared two species from the same site, demonstrated that while pink pine's growth was mainly influenced by summer temperatures, Libocedrus bidwillii was affected by conditions at the beginning of the growing season. However, the temperature signal in Westland's Libocedrus bidwillii was insufficient to produce a reliable reconstruction. It might be because the climate signal in this species was obscured by disturbances, as was shown in the final section of this project. Frequent growth releases and suppressions implied that Libocedrus bidwillii integrated both major (Alpine Fault earthquakes) and minor (windthrow) disturbances in its ring widths. Pink pine, on the other hand, was not sensitive to disturbance, and was therefore a better indicator of palaeotemperatures in Westland.
This research has strengthened the New Zealand network of chronology sites, and confirmed that pink pine has great dendroclimatic value. The last 520 years of temperature fluctuations were reconstructed with a high degree of fidelity - the model developed in this thesis is currently the most accurate estimate of a temperature-growth relationship in the country.
Cats all over the world hunt wild animals and can contribute to the extinction of threatened species. In New Zealand, around half of all households have at least one cat. When cats live close to a natural area, such as a wetland, they may have impacts on native species. A previous study on the movements and hunting behaviour of domestic (house) cats around the Travis Wetland, Christchurch, New Zealand during 2000-2001 raised concerns about the effects of cats on the local skink population, as skinks were a frequent prey item. My study is a comparison to the prior study, to determine if impacts have changed alongside changes in human populations in the area post-earthquake. The domestic cat population in the area was estimated by a household survey in March-April 2018. For a 6 month period from March-September 2018, 26 households recorded prey brought home by their 41 cats. During April-July 2018, 14 cats wore Global Positioning System (GPS) devices for 7 days each to track their movements. Skink abundance was measured with pitfall trapping over 20 days in February 2018. There were more households in the area in 2018 than there were in 2000, but the numbers of cats had decreased. In the 196 ha study area around Travis Wetland, the domestic cat population was estimated at 429 cats, down from the previous 494. Most of the cats were free roaming, but the majority had been desexed and many were mostly seen at home. A total of 42 prey items were reported from 26 households and 41 cats over 6 months. Of these, 62% were rodents, 26% were exotic birds, and 12% were native birds. There were no native skinks, other mammals, or other vertebrates such as fish and amphibians (invertebrates were not included in this study). Eight male and six female cats were tracked by GPS. Home range sizes for the 100% minimum convex polygons (MCPs) ranged from 1.34 to 9.68 ha (mean 4.09 ha, median 3.54 ha). There were 9/14 (64%) cats that entered the edge of the wetland. Males had significantly larger home range areas at night and in general compared with females. However, age and distance of the cat’s household to the wetland did not have a significant effect on home range size and there was no significant correlation between home range size and prey retrieved. In 20 days of skink trapping, 11 Oligosoma polychroma were caught. The estimated catch rate was not significantly different from an earlier study on skink abundance in Travis Wetland. The apparently low abundance of skinks may have been the result of successful wetland restoration creating less suitable skink habitat, or of other predators other than cats. In the future, increased education should be provided to the public about ways to increase wildlife in their area. This includes creating lizard friendly habitat in their gardens and increasing management for cats. Generally, only a few cats bring home prey often, and these select cats should be identified in initial surveys and included in further studies. In New Zealand, until management programmes can target all predators in urban areas, domestic cats could stay out at night and inside during the day to help decrease the abundance of rodents at night and reduce the number of birds and lizards caught during the day.
Abstract The original intention for the Partnership Community Worker (PCW) project in 2006 was for it to be an extension of the Pegasus Health General Practice and furthermore to be a bridge between the community and primary healthcare. It was believed that a close working relationship between the Practice Nurse and the PCW would help the target population of Māori, Pacifica and low income people to address and overcome their perceived barriers to healthcare which included: finance, transport, anxiety, cultural issues, communication, or lack of knowledge. Seven years later although the PCW project has been deemed a success in the Canterbury District Health Board annual reports (2013-14) and community and government agencies, including the Christchurch Resettlement Service (2012), many of the Pegasus Health General Practices have not utilised the project to its full extent, hence the need for this research. I was interested in finding out in the first instance if the model had changed and, if so why, and in the second instance if the promotional material currently distributed by Pegasus Health Primary Health Organisation reflected the daily practice of the PCW. A combination of methods were used including: surveys to the Pegasus Health General Practices, interviews with PCWs, interviews with managers of both the PCW host organisations and referring agencies to the PCW project. All the questions asked of all the participants in this research were focussed on their own perception of the role of the PCW. Results showed that the model has changed and although the publications were not reflecting the original intention of the project they did reflect the daily practice of the PCWs who are now struggling to meet much wider community expectations and needs. Key Results: Partnership Community Worker (PCW) interviews: Seventeen PCWs of the 19 employed were interviewed face to face. A number expressed interest in more culturally specific training and some are pursuing qualifications in social work; for many pay parity is an issue. In addition, many felt overwhelmed by the expectations around clients with mental health issues and housing issues now, post-earthquakes. Medical Practice surveys: Surveys were sent to eighty-two Pegasus Health medical practices and of these twenty five were completed. Results showed the full capacity of the PCW role was not clearly understood by all with many believing it was mostly a transport service. Those who did understand the full complexity of the role were very satisfied with the outcomes. PCW Host Community Manager Interviews: Of the ten out of twelve managers interviewed, some wished for more communication with Pegasus Health management because they felt aspects of both the PCW role and their own role as managers had become blurred over time. Referring organisations: Fifteen of the fifty referring community or government organisations participated. The overall satisfaction of the service was high and some acknowledged the continuing need for PCWs to be placed in communities where they were well known and trusted. Moreover results also showed that both the Canterbury earthquakes 2010-2011 and the amalgamation of Partnership Health PHO and Pegasus Health Charitable Limited in 2013 have contributed to the change of the model. Further future research may also be needed to examine the long term effects on the people of Canterbury involved in community work during the 2011-2014 years.
Spatial variations in river facies exerted a strong influence on the distribution of liquefaction features observed in Christchurch during the 2010-11 Canterbury Earthquake Sequence (CES). Liquefaction and liquefaction-induced ground deformation was primarily concentrated near modern waterways and areas underlain by Holocene fluvial deposits with shallow water tables (< 1 to 2 m). In southern Christchurch, spatial variations of liquefaction and subsidence were documented in the suburbs within inner meander loops of the Heathcote River. Newly acquired geospatial data, geotechnical reports and eye-witness discussions are compiled to provide a detailed account of the surficial effects of CES liquefaction and ground deformation adjacent to the Heathcote River. LiDAR data and aerial photography are used to produce a new series of original figures which reveal the locations of recurrent liquefaction and subsidence. To investigate why variable liquefaction patterns occurred, the distribution of surface ejecta and associated ground damage is compared with near-surface sedimentologic, topographic, and geomorphic variability to seek relationships between the near-surface properties and observed ground damages. The most severe liquefaction was concentrated within a topographic low in the suburb of St Martins, an inner meander loop of the Heathcote River, with liquefaction only minor or absent in the surrounding areas. Subsurface investigations at two sites in St Martins enable documentation of fluvial stratigraphy, the expressions of liquefaction, and identification of pre-CES liquefaction features. Excavation to water table depths (~1.5 m below the surface) across sand boils reveals multiple generations of CES liquefaction dikes and sills that cross-cut Holocene fluvial and anthropogenic stratigraphy. Based on in situ geotechnical tests (CPT) indicating sediment with a factor of safety < 1, the majority of surface ejecta was sourced from well-sorted fine to medium sand at < 5 m depth, with the most damaging liquefaction corresponding with the location of a low-lying sandy paleochannel, a remnant river channel from the Holocene migration of the meander in St Martins. In the adjacent suburb of Beckenham, where migration of the Heathcote River has been laterally confined by topography associated with the volcanic lithologies of Banks Peninsula, severe liquefaction was absent with only minor sand boils occurring closest to the modern river channel. Auger sampling across the suburb revealed thick (>1 m) clay-rich overbank and back swamp sediments that produced a stratigraphy which likely confined the units susceptible to liquefaction and prevented widespread ejection of liquefied material. This analysis suggests river migration promotes the formation and preservation of fluvial deposits prone to liquefaction. Trenching revealed the strongest CES earthquakes with large vertical accelerations favoured sill formation and severe subsidence at highly susceptible locations corresponding with an abandoned channel. Less vulnerable sites containing deeper and thinner sand bodies only liquefied in the strongest and most proximal earthquakes forming minor localised liquefaction features. Liquefaction was less prominent and severe subsidence was absent where lateral confinement of a Heathcote meander has promoted the formation of fluvial stratum resistant to liquefaction. Correlating CES liquefaction with geomorphic interpretations of Christchurch’s Heathcote River highlights methods in which the performance of liquefaction susceptibility models can be improved. These include developing a reliable proxy for estimating soil conditions in meandering fluvial systems by interpreting the geology and geomorphology, derived from LiDAR data and modern river morphology, to improve the methods of accounting for the susceptibility of an area. Combining geomorphic interpretations with geotechnical data can be applied elsewhere to identify regional liquefaction susceptibilities, improve existing liquefaction susceptibility datasets, and predict future earthquake damage.
Many contemporary urban communities are challenged by increased flood risks and rising temperatures, declining water quality and biodiversity, and reduced mental, physical, cultural and social wellbeing. The development of urban blue-green infrastructure (BGI), defined as networks of natural and semi-natural blue-green spaces which enable healthy ecosystem processes, has been identified as one approach to mitigate these challenges and enable more liveable cities. Multiple benefits associated with urban BGI have been identified, including reduced flood risk and temperatures, improved water quality and biodiversity, enhanced mental and physical wellbeing, strengthened social cohesion and sense of place, and the facilitation of cultural connections and practices. However, socio-cultural benefits have tended to be neglected in BGI research and design, resulting in a lack of awareness of how they may be maximised in BGI design. As such, this research sought to understand how BGI can best be designed to enable liveable cities. Four questions were considered: (i) what benefits are associated with urban BGI, (ii) how does the design process influence the benefits achieved by BGI, (iii) what challenges are encountered during BGI design, and (iv) how might the incorporation of communities and Indigenous knowledge into BGI research and design enhance current understandings and applications of urban BGI? To address these questions, a mixed methods case study approach was employed in Ōtautahi Christchurch and Kaiapoi. The four selected case studies were Te Oranga Waikura, Wigram Basin, Te Kuru and the Kaiapoi Honda Forest. The cases are all council owned urban wetlands which were primarily designed or retrofitted to reduce urban flood risks following the Canterbury Earthquake Sequence. To investigate BGI design processes in each case, as well as how communities interact with, value and benefit from these spaces. BGI projects were found to be designed by interdisciplinary design teams driven by stormwater engineers, landscape architects and ecologists which prioritised bio-physical outcomes. Further, community and Indigenous engagement approaches closely resembled consultation, with the exception of Te Kuru which employed a co-design approach between councils and Indigenous and community groups. This co-design approach was found to enhance current understandings and applications of urban BGI, while uncovering multiple socio-cultural values to be incorporated into design, such as access to cultural healing resources, increased community connections to water, and facilitating cultural monitoring methodologies and citizen science initiatives. Communities frequently identified the opportunity to connect with natural environments and enhanced mental and physical wellbeing as key benefits of BGI. Conversely, strengthened social cohesion, sense of place and cultural connections were infrequently identified as benefits, if at all. This finding indicates a disconnect between the bio-physical benefits which drive BGI design and the outcomes which communities value. As such, there is a need for future BGI design to more fully consider and design for socio- cultural outcomes to better enable liveable cities. To better design BGI to enhance urban liveability, this research makes three key contributions. First, there is a need to advance current approaches to transdisciplinary design to better account for the full scope of perspectives and values associated with BGI. Second, there is a need to transition towards relational co-design with Indigenous and community groups and knowledge. Third, it is important to continue to monitor, reflect on and share both positive and negative BGI design experiences to continually improve outcomes. The incorporation of social and cultural researchers, knowledges and perspectives into open and collaborative transdisciplinary design teams is identified as a key method to achieve these opportunities.
The demand for a new approach to safeguarding New Zealand’s endangered historic buildings was identified as a result of the recent increase in building code and strengthening requirements following the Christchurch earthquakes of 2010-2011. The Wellington City Council identified 266 heritage buildings in the city that must be either strengthened or demolished to address these increased requirements. This thesis explores this threat as an opportunity for researching how contemporary design interventions can be challenged to both strengthen and become active participants in the ongoing history of New Zealand’s potentially endangered historic buildings. This thesis challenges the current approach of completely ‘restoring’ 19th-20th century historic buildings in New Zealand, to develop techniques that structurally reinforce historic buildings while inviting the progressive weathering of a building to remain as a testament to its history. This thesis proposes a structural intervention that is responsive to the progressive history of historic buildings, simultaneously introducing a contemporary structural intervention that both participates in and compliments the progressive historic transformations of the vehicle. This thesis argues that current historic buildings in semi-decayed states in fact enable visitors to witness multiple stages in the life of a building, while fully restored buildings only enable visitors to witness the original form of the building. This thesis proposes a model for contemporary intervention within historic buildings that draws a design intervention from seismic strengthening.The notion of layering is explored as a design approach to incorporate the contemporary with the historic as an additional layer of exposed on-going history, thereby further exposing the layers of history evident within New Zealand’s historic buildings. This thesis combines layering theories of architects Louis Kahn and Carlo Scarpa with related theories of installation artist Mary Miss. The theoretical imperatives of Scarpa and Kahn are explored as a tool of engagement for the junction between the contemporary and historic building materials, and the work of Marry Miss is explored as a design approach for developing a contemporary intervention that references the layered historic building while inviting new means of occupancy between layers. The selected vehicle for the design research investigation is the Albemarle Hotel on Ghuznee Street in Wellington. The techniques proposed in this thesis to strengthen the Albemarle Hotel suggest an approach that might be applied to New Zealand’s wider body of historic buildings that constitute New Zealand’s heritage fabric, ultimately protecting them from demolition while preserving additional layers of their historic narratives. Over all the design research experiments suggest that contemporary interventions derived from structural strengthening may be a viable and cost-effective method of re-inhabiting New Zealand’s endangered heritage buildings, avoiding demolition and securing New Zealand’s heritage for future generations. Research Questions: This thesis challenges the current economically unsustainable approach of laterally reinforcing and completely ‘restoring’ 19th-20th century historic buildings in New Zealand. This thesis argues that current historic buildings in semi-decayed states in fact enable visitors to witness multiple stages in the on-going life of a building. Can the weathered state of New Zealand's heritage buildings be proactively retained and celebrated as witnesses to their history? Can new lateral reinforcing requirements be conceived as active participants in revealing the on-going history of New Zealand's historic buildings?
The research presented in this thesis investigated the environmental impacts of structural design decisions across the life of buildings located in seismic regions. In particular, the impacts of expected earthquake damage were incorporated into a traditional life cycle assessment (LCA) using a probabilistic method, and links between sustainable and resilient design were established for a range of case-study buildings designed for different seismic performance objectives. These links were quantified using a metric herein referred to as the seismic carbon risk, which represents the expected environmental impacts and resource use indicators associated with earthquake damage during buildings’ life. The research was broken into three distinct parts: (1) a city-level evaluation of the environmental impacts of demolitions following the 2010/2011 Canterbury earthquake sequence in New Zealand, (2) the development of a probabilistic framework to incorporate earthquake damage into LCA, and (3) using case-study buildings to establish links between sustainable and resilient design. The first phase of the research focused on the environmental impacts of demolitions in Christchurch, New Zealand following the 2010/2011 Canterbury Earthquake Sequence. This large case study was used to investigate the environmental impact of the demolition of concrete buildings considering the embodied carbon and waste stream distribution. The embodied carbon was considered here as kilograms of CO2 equivalent that occurs on production, construction, and waste management stage. The results clearly demonstrated the significant environmental impacts that can result from moderate and large earthquakes in urban areas, and the importance of including environmental considerations when making post-earthquake demolition decisions. The next phase of the work introduced a framework for incorporating the impacts of expected earthquake damage based on a probabilistic approach into traditional LCA to allow for a comparison of seismic design decisions using a carbon lens. Here, in addition to initial construction impacts, the seismic carbon risk was quantified, including the impacts of seismic repair activities and total loss scenarios assuming reconstruction in case of non-reparability. A process-based LCA was performed to obtain the environmental consequence functions associated with structural and non-structural repair activities for multiple environmental indicators. In the final phase of the work, multiple case-study buildings were used to investigate the seismic consequences of different structural design decisions for buildings in seismic regions. Here, two case-study buildings were designed to multiple performance objectives, and the upfront carbon costs, and well as the seismic carbon risk across the building life were compared. The buildings were evaluated using the framework established in phase 2, and the results demonstrated that the seismic carbon risk can significantly be reduced with only minimal changes to the upfront carbon for buildings designed for a higher base shear or with seismic protective systems. This provided valuable insight into the links between resilient and sustainable design decisions. Finally, the results and observations from the work across the three phases of research described above were used to inform a discussion on important assumptions and topics that need to be considered when quantifying the environmental impacts of earthquake damage on buildings. These include: selection of a non-repairable threshold (e.g. a value beyond which a building would be demolished rather than repaired), the time value of carbon (e.g. when in the building life the carbon is released), the changing carbon intensity of structural materials over time, and the consideration of deterministic vs. probabilistic results. Each of these topics was explored in some detail to provide a clear pathway for future work in this area.
Timber has experienced renewed interests as a sustainable building material in recent times. Although traditionally it has been the prime choice for residential construction in New Zealand and some other parts of the world, its use can be increased significantly in the future through a wider range of applications, particularly when adopting engineered wood material, Research has been started on the development of innovative solutions for multi-storey non-residential timber buildings in recent years and this study is part of that initiative. Application of timber in commercial and office spaces posed some challenges with requirements of large column-free spaces. The current construction practice with timber is not properly suited for structures with the aforementioned required characteristics and new type of structures has to be developed for this type of applications. Any new structural system has to have adequate capacity for carry the gravity and lateral loads due to occupancy and the environmental effects. Along with wind loading, one of the major sources of lateral loads is earthquakes. New Zealand, being located in a seismically active region, has significant risk of earthquake hazard specially in the central region of the country and any structure has be designed for the seismic loading appropriate for the locality. There have been some significant developments in precast concrete in terms of solutions for earthquake resistant structures in the last decade. The “Hybrid” concept combining post-tensioning and energy dissipating elements with structural members has been introduced in the late 1990s by the precast concrete industry to achieve moment-resistant connections based on dry jointed ductile connections. Recent research at the University of Canterbury has shown that the concept can be adopted for timber for similar applications. Hybrid timber frames using post-tensioned beams and dissipaters have the potential to allow longer spans and smaller cross sections than other forms of solid timber frames. Buildings with post-tensioned frames and walls can have larger column-free spaces which is a particular advantage for non-residential applications. While other researchers are focusing on whole structural systems, this research concentrated on the analysis and design of individual members and connections between members or between member and foundation. This thesis extends existing knowledge on the seismic behaviour and response of post-tensioned single walls, columns under uni-direction loads and small scale beam-column joint connections into the response and design of post-tensioned coupled walls, columns under bi-directional loading and full-scale beam-column joints, as well as to generate further insight into practical applications of the design concept for subassemblies. Extensive experimental investigation of walls, column and beam-column joints provided valuable confirmation of the satisfactory performance of these systems. In general, they all exhibited almost complete re-centering capacity and significant energy dissipation, without resulting into structural damage. The different configurations tested also demonstrated the flexibility in design and possibilities for applications in practical structures. Based on the experimental results, numerical models were developed and refined from previous literature in precast concrete jointed ductile connections to predict the behaviour of post-tensioned timber subassemblies. The calibrated models also suggest the values of relevant parameters for applications in further analysis and design. Section analyses involving those parameters are performed to develop procedures to calculate moment capacities of the subassemblies. The typical features and geometric configurations the different types of subassemblies are similar with the only major difference in the connection interfaces. With adoption of appropriate values representing the corresponding connection interface and incorporation of the details of geometry and configurations, moment capacities of all the subassemblies can be calculated with the same scheme. That is found to be true for both post-tensioned-only and hybrid specimens and also applied for both uni-directional and bi-directional loading. The common section analysis and moment capacity calculation procedure is applied in the general design approach for subassemblies.
The increase of the world's population located near areas prone to natural disasters has given rise to new ‘mega risks’; the rebuild after disasters will test the governments’ capabilities to provide appropriate responses to protect the people and businesses. During the aftermath of the Christchurch earthquakes (2010-2012) that destroyed much of the inner city, the government of New Zealand set up a new partnership between the public and private sector to rebuild the city’s infrastructure. The new alliance, called SCIRT, used traditional risk management methods in the many construction projects. And, in hindsight, this was seen as one of the causes for some of the unanticipated problems. This study investigated the risk management practices in the post-disaster recovery to produce a specific risk management model that can be used effectively during future post-disaster situations. The aim was to develop a risk management guideline for more integrated risk management and fill the gap that arises when the traditional risk management framework is used in post-disaster situations. The study used the SCIRT alliance as a case study. The findings of the study are based on time and financial data from 100 rebuild projects, and from surveying and interviewing risk management professionals connected to the infrastructure recovery programme. The study focussed on post-disaster risk management in construction as a whole. It took into consideration the changes that happened to the people, the work and the environment due to the disaster. System thinking, and system dynamics techniques have been used due to the complexity of the recovery and to minimise the effect of unforeseen consequences. Based on an extensive literature review, the following methods were used to produce the model. The analytical hierarchical process and the relative importance index have been used to identify the critical risks inside the recovery project. System theory methods and quantitative graph theory have been used to investigate the dynamics of risks between the different management levels. Qualitative comparative analysis has been used to explore the critical success factors. And finally, causal loop diagrams combined with the grounded theory approach has been used to develop the model itself. The study identified that inexperienced staff, low management competency, poor communication, scope uncertainty, and non-alignment of the timing of strategic decisions with schedule demands, were the key risk factors in recovery projects. Among the critical risk groups, it was found that at a strategic management level, financial risks attracted the highest level of interest, as the client needs to secure funding. At both alliance-management and alliance-execution levels, the safety and environmental risks were given top priority due to a combination of high levels of emotional, reputational and media stresses. Risks arising from a lack of resources combined with the high volume of work and the concern that the cost could go out of control, alongside the aforementioned funding issues encouraged the client to create the recovery alliance model with large reputable construction organisations to lock in the recovery cost, at a time when the scope was still uncertain. This study found that building trust between all parties, clearer communication and a constant interactive flow of information, established a more working environment. Competent and clear allocation of risk management responsibilities, cultural shift, risk prioritisation, and staff training were crucial factors. Finally, the post-disaster risk management (PDRM) model can be described as an integrated risk management model that considers how the changes which happened to the environment, the people and their work, caused them to think differently to ease the complexity of the recovery projects. The model should be used as a guideline for recovery systems, especially after an earthquake, looking in detail at all the attributes and the concepts, which influence the risk management for more effective PDRM. The PDRM model is represented in Causal Loops Diagrams (CLD) in Figure 8.31 and based on 10 principles (Figure 8.32) and 26 concepts (Table 8.1) with its attributes.
The overarching goal of this dissertation is to improve predictive capabilities of geotechnical seismic site response analyses by incorporating additional salient physical phenomena that influence site effects. Specifically, multidimensional wave-propagation effects that are neglected in conventional 1D site response analyses are incorporated by: (1) combining results of 3D regional-scale simulations with 1D nonlinear wave-propagation site response analysis, and (2) modelling soil heterogeneity in 2D site response analyses using spatially-correlated random fields to perturb soil properties. A method to combine results from 3D hybrid physics-based ground motion simulations with site-specific nonlinear site response analyses was developed. The 3D simulations capture 3D ground motion phenomena on a regional scale, while the 1D nonlinear site response, which is informed by detailed site-specific soil characterization data, can capture site effects more rigorously. Simulations of 11 moderate-to-large earthquakes from the 2010-2011 Canterbury Earthquake Sequence (CES) at 20 strong motion stations (SMS) were used to validate simulations with observed ground motions. The predictions were compared to those from an empirically-based ground motion model (GMM), and from 3D simulations with simplified VS30- based site effects modelling. By comparing all predictions to observations at seismic recording stations, it was found that the 3D physics-based simulations can predict ground motions with comparable bias and uncertainty as the GMM, albeit, with significantly lower bias at long periods. Additionally, the explicit modelling of nonlinear site-response improves predictions significantly compared to the simplified VS30-based approach for soft-soil or atypical sites that exhibit exceptionally strong site effects. A method to account for the spatial variability of soils and wave scattering in 2D site response analyses was developed and validated against a database of vertical array sites in California. The inputs required to run the 2D analyses are nominally the same as those required for 1D analyses (except for spatial correlation parameters), enabling easier adoption in practice. The first step was to create the platform and workflow, and to perform a sensitivity study involving 5,400 2D model realizations to investigate the influence of random field input parameters on wave scattering and site response. Boundary conditions were carefully assessed to understand their effect on the modelled response and select appropriate assumptions for use on a 2D model with lateral heterogeneities. Multiple ground-motion intensity measures (IMs) were analyzed to quantify the influence from random field input parameters and boundary conditions. It was found that this method is capable of scattering seismic waves and creating spatially-varying ground motions at the ground surface. The redistribution of ground-motion energy across wider frequency bands, and the scattering attenuation of high-frequency waves in 2D analyses, resemble features observed in empirical transfer functions (ETFs) computed in other studies. The developed 2D method was subsequently extended to more complicated multi-layer soil profiles and applied to a database of 21 vertical array sites in California to test its appropriate- ness for future predictions. Again, different boundary condition and input motion assumptions were explored to extend the method to the in-situ conditions of a vertical array (with a sensor embedded in the soil). ETFs were compared to theoretical transfer functions (TTFs) from conventional 1D analyses and 2D analyses with heterogeneity. Residuals of transfer-function- based IMs, and IMs of surface ground motions, were also used as validation metrics. The spatial variability of transfer-function-based IMs was estimated from 2D models and compared to the event-to-event variability from ETFs. This method was found capable of significantly improving predictions of median ETF amplification factors, especially for sites that display higher event-to-event variability. For sites that are well represented by 1D methods, the 2D approach can underpredict amplification factors at higher modes, suggesting that the level of heterogeneity may be over-represented by the 2D random field models used in this study.
The Avon-Heathcote Estuary, located in Christchurch, New Zealand, experienced coseismic deformation as a result of the February 22nd 2011 Christchurch Earthquake. The deformation is reflected as subsidence in the northern area and uplift in the southern area of the Estuary, in addition to sand volcanoes which forced up sediment throughout the floor of the Estuary altering estuary bed height and tidal flow. The first part of the research involved quantifying the change in the modern benthic foraminifera distribution as a result of the coseismic deformation caused by the February 22nd 2011 earthquake. By analysing the taxa present immediately post deformation and then the taxa present 2 years post deformation a comparison of the benthic foraminifera distribution can be made of the pre and post deformation. Both the northern and the southern areas of the Estuary were sampled to establish whether foraminifera faunas migrated landward or seaward as a result of subsidence and uplift experienced in different areas. There was no statistical change in overall species distribution in the two year time period since the coseismic deformation occurred, however, there were some noticeable changes in foraminifera distribution at BSNS-Z3 showing a landward migration of taxa. The changes that were predicted to occur as a result of the deformation of the Estuary are taking longer than expected to show up in the foraminiferal record and a longer time period is needed to establish these changes. The second stage involved establishing the modern distribution of foraminifera at Settlers Reserve in the southern area of the Avon-Heathcote Estuary by detailed sampling along a 160 m transect. Foraminifera are sensitive to environmental parameters, tidal height, grainsize, pH and salinity were recorded to evaluate the effect these parameters have on distribution. Bray-Curtis two-way cluster analysis was primarily used to assess the distribution pattern of foraminifera. The modern foraminifera distribution is comparable to that of the modern day New Zealand brackish-water benthic foraminifera distribution and includes species not yet found in other studies of the Avon-Heathcote Estuary. Differences in sampling techniques and the restricted intertidal marshland area where the transect samples were collected account for some of the differences seen between this model and past foraminifera studies. xiii The final stage involved sampling a 2.20 m core collected from Settlers Reserve and using the modern foraminiferal distribution to establish a foraminiferal history of Settlers Reserve. As foraminifera are sensitive to tidal height they may record past coseismic deformation events and the core was used to ascertain whether record of past coseismic deformation is preserved in Settlers Reserve sediments. Sampling the core for foraminifera, grainsize, trace metals and carbon material helped to build a story of estuary development. Using the modern foraminiferal distribution and the tidal height information collected, a down core model of past tidal heights was established to determine past rates of change. Foraminifera are not well preserved throughout the core, however, a sudden relative rise in sea level is recorded between 0.25 m and 0.85 m. Using trace metal and isotope analysis to develop an age profile, this sea level rise is interpreted to record coseismic subsidence associated with a palaeoseismic event in the early 1900’s. Overall, although the Avon-Heathcote Estuary experienced clear coseismic deformation as a result of the 22nd of February 2011 earthquake, modern changes in foraminiferal distribution cannot yet be tracked, however, past seismic deformation is identified in a core. The modern transect describes the foraminifera distribution which identifies species that have not been identified in the Avon-Heathcote Estuary before. This thesis enhances the current knowledge of the Avon-Heathcote Estuary and is a baseline for future studies.
Christchurch City Council (Council) is undertaking the Land Drainage Recovery Programme in order to assess the effects of the earthquakes on flood risk to Christchurch. In the course of these investigations it has become better understood that floodplain management should be considered in a multi natural hazards context. Council have therefore engaged the Jacobs, Beca, University of Canterbury, and HR Wallingford project team to investigate the multihazards in eastern areas of Christchurch and develop flood management options which also consider other natural hazards in that context (i.e. how other hazards contribute to flooding both through temporal and spatial coincidence). The study has three stages: Stage 1 Gap Analysis – assessment of information known, identification of gaps and studies required to fill the gaps. Stage 2 Hazard Studies – a gap filling stage with the studies identified in Stage 1. Stage 3 Collating, Optioneering and Reporting – development of options to manage flood risk. This present report is to document findings of Stage 1 and recommends the studies that should be completed for Stage 2. It has also been important to consider how Stage 3 would be delivered and the gaps are prioritised to provide for this. The level of information available and hazards to consider is extensive; requiring this report to be made up of five parts each identifying individual gaps. A process of identifying information for individual hazards in Christchurch has been undertaken and documented (Part 1) followed by assessing the spatial co-location (Part 2) and probabilistic presence of multi hazards using available information. Part 3 considers multi hazard presence both as a temporal coincidence (e.g. an earthquake and flood occurring at one time) and as a cascade sequence (e.g. earthquake followed by a flood at some point in the future). Council have already undertaken a number of options studies for managing flood risk and these are documented in Part 4. Finally Part 5 provides the Gap Analysis Summary and Recommendations to Council. The key findings of Stage 1 gap analysis are: - The spatial analysis showed eastern Christchurch has a large number of hazards present with only 20% of the study area not being affected by any of the hazards mapped. Over 20% of the study area is exposed to four or more hazards at the frequencies and data available. - The majority of the Residential Red Zone is strongly exposed to multiple hazards, with 86% of the area being exposed to 4 or more hazards, and 24% being exposed to 6 or more hazards. - A wide number of gaps are present; however, prioritisation needs to consider the level of benefit and risks associated with not undertaking the studies. In light of this 10 studies ranging in scale are recommended to be done for the project team to complete the present scope of Stage 3. - Stage 3 will need to consider a number of engineering options to address hazards and compare with policy options; however, Council have not established a consistent policy on managed retreat that can be applied for equal comparison; without which substantial assumptions are required. We recommend Council undertake a study to define a managed retreat framework as an option for the city. - In undertaking Stage 1 with floodplain management as the focal point in a multi hazards context we have identified that Stage 3 requires consideration of options in the context of economics, implementation and residual risk. Presently the scope of work will provide a level of definition for floodplain options; however, this will not be at equal levels of detail for other hazard management options. Therefore, we recommend Council considers undertaking other studies with those key hazards (e.g. Coastal Hazards) as a focal point and identifies the engineering options to address such hazards. Doing so will provide equal levels of information for Council to make an informed and defendable decision on which options are progressed following Stage 3.
Saltwater Forest is a Dacrydium cupressinum-dominated lowland forest covering 9000 ha in south Westland, South Island, New Zealand. Four thousand hectares is managed for sustainable production of indigenous timber. The aim of this study was to provide an integrated analysis of soils, soil-landform relationships, and soil-vegetation relationships at broad and detailed scales. The broad scale understandings provide a framework in which existing or future studies can be placed and the detailed studies elucidate sources of soil and forest variability.
Glacial landforms dominate. They include late Pleistocene lateral, terminal and ablation moraines, and outwash aggradation and degradation terraces. Deposits and landforms from six glacial advances have been recognised ranging from latest Last (Otira) Glaciation to Penultimate (Waimea) Glaciation. The absolute ages of landforms were established by analysis of the thickness and soil stratigraphy of loess coverbeds, augmented with radiocarbon dating and phytolith and pollen analysis.
In the prevailing high rainfall of Westland soil formation is rapid. The rate of loess accretion in Saltwater
Forest (ca. 30 mm ka⁻¹) has been low enough that soil formation and loess accretion took place contemporaneously. Soils formed in this manner are known as upbuilding soils. The significant difference between upbuilding pedogenesis and pedogenesis in a topdown sense into an existing sediment body is that each subsoil increment of an upbuilding soil has experienced processes of all horizons above. In Saltwater Forest subsoils of upbuilding soils are strongly altered because they have experienced the extremely acid environment of the soil surface at some earlier time. Some soil chronosequence studies in Westland have included upbuilding soils formed in loess as the older members of the sequence. Rates and types of processes inferred from these soils should be reviewed because upbuilding is a different pedogenic pathway to topdown pedogenesis.
Landform age and morphology were used as a primary stratification for a study of the soil pattern and nature of soil variability in the 4000 ha production area of Saltwater Forest. The age of landforms (> 14 ka) and rapid soil formation mean that soils are uniformly strongly weathered and leached. Soils include Humic Organic Soils, Perch-gley Podzols, Acid Gley Soils, Allophanic Brown Soils, and Orthic or Pan Podzols. The major influence on the nature of soils is site hydrology which is determined by macroscale features of landforms (slope, relief, drainage density), mesoscale effects related to position on landforms, and microscale influences determined by microtopography and individual tree effects. Much of the soil variability arises at microscales so that it is not possible to map areas of uniform soils at practical map scales. The distribution of soil variability across spatial scales, in relation to the intensity of forest management, dictates that it is most appropriate to map soil complexes with boundaries coinciding with landforms.
Disturbance of canopy trees is an important agent in forest dynamics. The frequency of forest disturbance in the production area of Saltwater Forest varies in a systematic way among landforms in accord with changes in abundance of different soils. The frequency of forest turnover is highest on landforms with the greatest abundance of extremely poorly-drained Organic Soils. As the abundance of better-drained soils increases the frequency of forest turnover declines. Changes in turnover frequency are reflected in the mean size and density of canopy trees (Dacrydium cupressinum) among landforms. Terrace and ablation moraine landforms with the greatest abundance of extremely poorly-drained soils have on average the smallest trees growing most densely. The steep lateral moraines, characterised by well drained soils, have fewer, larger trees. The changes manifested at the landform scale are an integration of processes operating over much shorter range as a result of short-range soil variability. The systematic changes in forest structure and turnover frequency among landforms and soils have important implications for sustainable forest management.
Research on responses to trauma has historically focused on the negative repercussions of a struggle with adversity. However, more recently, researchers have begun to examine posttraumatic growth: the positive psychological change that emerges from the struggle with a potentially traumatic event. Associations have been found between posttraumatic growth and greater peritraumatic distress, greater objective severity of trauma exposure, greater perceived stressfulness of events, social support, female gender, cognitive and behavioural responses to trauma, and personality measures. Posttraumatic growth has been measured typically in individuals with varying levels of posttraumatic stress disorder symptoms and other psychological difficulties, such as depression and anxiety. Although some theory and research posits that higher resilience would prohibit posttraumatic growth, no studies have examined posttraumatic growth in a resilient sample. The Canterbury earthquake sequence of 2010 and 2011 involved potentially traumatic events that saw the community struggle with a variety of challenges. However, in the midst of earthquake destruction, some positive initiatives emerged, driven by locals. The Gap Filler project (using city spaces left empty from fallen buildings for art and interactive community projects) and the Student Volunteer Army (groups of volunteers coordinated to help others in need) are examples of this. In this context, it seemed likely that posttraumatic growth was occurring and might be seen in individuals who were coping well with challenges. Culture is theorised to influence the posttraumatic growth process (Calhoun, Cann, & Tedeschi, 2010), and the nature of the trauma undergone is also likely to influence the process of growth. The current thesis measures posttraumatic growth quantitatively and qualitatively in a New Zealand sample. It measures and describes posttraumatic growth in a resilient population after the earthquake sequence of 2010 and 2011 in Canterbury, New Zealand. Findings are used to test current models of posttraumatic growth for individuals coping well after trauma and to elaborate on mechanisms proposed by models such as the comprehensive model of posttraumatic growth (Calhoun et al., 2010) and the organismic valuing theory of growth through adversity (Joseph & Linley, 2005). Correlates of posttraumatic growth are examined and likely supporting factors of posttraumatic growth are identified for this population. Study 1 used quantitative analysis to explore correlates of posttraumatic growth and found that greater posttraumatic growth related to greater peritraumatic distress, greater perceived stressfulness of earthquake events, greater objective stressfulness of earthquake events, greater difficulty with stressful life events, less satisfaction with social support, and female gender. Findings from Study 1 give important detail about the nature of distress included in the comprehensive model of posttraumatic growth (Calhoun et al., 2010) for this population. Levels of posttraumatic growth were lower than those in North American studies but similar to those in a Chinese study. The current sample, however, showed lower endorsement of Relating to Others than the Chinese study, perhaps because of cultural differences. Study 2 used qualitative analysis to examine the experience of posttraumatic growth in the sample. The theme of ‘a greater sense of community’ was found and adds to the comprehensive model of posttraumatic growth, in that an expression of posttraumatic growth (a greater connection with others) can inform ongoing social processing in the posttraumatic growth process. Having a formal or informal role in earthquake recovery appeared to influence self-concept and reflection; this elaborates on the influence of role on reflection in Calhoun et al.’s model. Findings illustrate possible mechanisms of the organismic valuing process theorised by Joseph and Linley (2005). Implications include the importance of providing opportunities for individuals to take on a role after a crisis, encouraging them to act to respond to difficulties, and encouraging them to meet personal needs for relatedness, competence, and autonomy. Finding positive aspects to a difficult situation, as well as acknowledging adversity, can be supported in future to help individuals process their traumas. As a society, we can help individuals cope with adversity by providing ways they can meet their needs for relatedness, competence, and autonomy. Community groups likely provide opportunities for members to act in ways that meet such needs. This will allow them to effectively act to meet their needs in times of crisis.
This dissertation addresses a diverse range of topics in the area of physics-based ground motion simulation with particular focus on the Canterbury, New Zealand region. The objectives achieved provide the means to perform hybrid broadband ground motion simulation and subsequently validates the simulation methodology employed. In particu- lar, the following topics are addressed: the development of a 3D seismic velocity model of the Canterbury region for broadband ground motion simulation; the development of a 3D geologic model of the interbedded Quaternary formations to provide insight on observed ground motions; and the investigation of systematic effects through ground motion sim- ulation of small-to-moderate magnitude earthquakes. The paragraphs below outline each contribution in more detail. As a means to perform hybrid broadband ground motion simulation, a 3D model of the geologic structure and associated seismic velocities in the Canterbury region is devel- oped utilising data from depth-converted seismic reflection lines, petroleum and water well logs, cone penetration tests, and implicitly guided by existing contour maps and geologic cross sections in data sparse subregions. The model explicitly characterises five significant and regionally recognisable geologic surfaces that mark the boundaries between geologic units with distinct lithology and age, including the Banks Peninsula volcanics, which are noted to strongly influence seismic wave propagation. The Basement surface represents the base of the Canterbury sedimentary basin, where a large impedance contrast exists re- sulting in basin-generated waves. Seismic velocities for the lithological units between the geologic surfaces are derived from well logs, seismic reflection surveys, root mean square stacking velocities, empirical correlations, and benchmarked against a regional crustal model, thus providing the necessary information for a Canterbury velocity model for use in broadband seismic wave propagation. A 3D high-resolution model of the Quaternary geologic stratigraphic sequence in the Canterbury region is also developed utilising datasets of 527 high-quality water well logs, and 377 near-surface cone penetration test records. The model, developed using geostatistical Kriging, represents the complex interbedded regional Quaternary geology by characterising the boundaries between significant interbedded geologic formations as 3D surfaces including explicit modelling of the formation unconformities resulting from the Banks Peninsula volcanics. The stratigraphic layering present can result in complex wave propagation. The most prevalent trend observed in the surfaces was the downward dip from inland to the eastern coastline as a result of the dominant fluvial depositional environment of the terrestrial gravel formations. The developed model provides a benefi- cial contribution towards developing a comprehensive understanding of recorded ground motions in the region and also providing the necessary information for future site char- acterisation and site response analyses. To highlight the practicality of the model, an example illustrating the role of the model in constraining surface wave analysis-based shear wave velocity profiling is illustrated along with the calculation of transfer functions to quantify the effect of the interbedded geology on wave propagation. Lastly, an investigation of systematic biases in the (Graves and Pitarka, 2010, 2015) ground motion simulation methodology and the specific inputs used for the Canterbury region is presented considering 144 small-to-moderate magnitude earthquakes. In the simulation of these earthquakes, the 3D Canterbury Velocity Model, developed as a part of this dissertation, is used for the low-frequency simulation, and a regional 1D velocity model for the high-frequency simulation. Representative results for individual earthquake sources are first presented to highlight the characteristics of the small-to-moderate mag- nitude earthquake simulations through waveforms, intensity measure scaling with source- to-site distance, and spectral bias of the individual events. Subsequently, a residual de- composition is performed to examine the between- and within-event residuals between observed data, and simulated and empirical predictions. By decomposing the residuals into between- and within-event residuals, the biases in source, path and site effects, and their causes, can be inferred. The residuals are comprehensively examined considering their aggregated characteristics, dependence on predictor variables, spatial distribution, and site-specific effects. The results of the simulation are also benchmarked against empir- ical ground motion models, where their similarities manifest from common components in their prediction. Ultimately, suggestions to improve the predictive capability of the simulations are presented as a result of the analysis.
Bulk rock strength is greatly dependent on fracture density, so that reductions in rock strength associated with faulting and fracturing should be reflected by reduced shear coupling and hence S-wave velocity. This study is carried out along the Canterbury rangefront and in Otago. Both lie within the broader plate boundary deformation zone in the South Island of New Zealand. Therefore built structures are often, , located in areas where there are undetected or poorly defined faults with associated rock strength reduction. Where structures are sited near to, or across, such faults or fault-zones, they may sustain both shaking and ground deformation damage during an earthquake. Within this zone, management of seismic hazards needs to be based on accurate identification of the potential fault damage zone including the likely width of off-plane deformation. Lateral S-wave velocity variability provides one method of imaging and locating damage zones and off-plane deformation. This research demonstrates the utility of Multi-Channel Analysis of Surface Waves (MASW) to aid land-use planning in such fault-prone settings. Fundamentally, MASW uses surface wave dispersive characteristics to model a near surface profile of S-wave velocity variability as a proxy for bulk rock strength. The technique can aid fault-zone planning not only by locating and defining the extent of fault-zones, but also by defining within-zone variability that is readily correlated with measurable rock properties applicable to both foundation design and the distribution of surface deformation. The calibration sites presented here have well defined field relationships and known fault-zone exposure close to potential MASW survey sites. They were selected to represent a range of progressively softer lithologies from intact and fractured Torlesse Group basement hard rock (Dalethorpe) through softer Tertiary cover sediments (Boby’s Creek) and Quaternary gravels. This facilitated initial calibration of fracture intensity at a high-velocity-contrast site followed by exploration of the limits of shear zone resolution at lower velocity contrasts. Site models were constructed in AutoCAD in order to demonstrate spatial correlations between S-wave velocity and fault zone features. Site geology was incorporated in the models, along with geomorphology, river profiles, scanline locations and crosshole velocity measurement locations. Spatial data were recorded using a total-station survey. The interpreted MASW survey results are presented as two dimensional snapshot cross-sections of the three dimensional calibration-site models. These show strong correlations between MASW survey velocities and site geology, geomorphology, fluvial profiles and geotechnical parameters and observations. Correlations are particularly pronounced where high velocity contrasts exist, whilst weaker correlations are demonstrated in softer lithologies. Geomorphic correlations suggest that off-plane deformation can be imaged and interpreted in the presence of suitable topographic survey data. A promising new approach to in situ and laboratory soft-rock material and mass characterisation is also presented using a Ramset nail gun. Geotechnical investigations typically involve outcrop and laboratory scale determination of rock mass and material properties such as fracture density and unconfined compressive strength (UCS). This multi-scale approach is espoused by this study, with geotechnical and S-wave velocity data presented at multiple scales, from survey scale sonic velocity measurements, through outcrop scale scanline and crosshole sonic velocity measurements to laboratory scale property determination and sonic velocity measurements. S-wave velocities invariably increased with decreasing scale. These scaling relationships and strategies for dealing with them are investigated and presented. Finally, the MASW technique is applied to a concealed fault on the Taieri Ridge in Macraes Flat, Central Otago. Here, high velocity Otago Schist is faulted against low velocity sheared Tertiary and Quaternary sediments. This site highlights the structural sensitivity of the technique by apparently constraining the location of the principal fault, which had been ambiguous after standard processing of the seismic reflection data. Processing of the Taieri Ridge dataset has further led to the proposal of a novel surface wave imaging technique termed Swept Frequency Imaging (SFI). This inchoate technique apparently images the detailed structure of the fault-zone, and is in agreement with the conventionally-determined fault location and an existing partial trench. Overall, the results are promising and are expected to be supported by further trenching in the near future.
Recent surface-rupturing earthquakes in New Zealand have highlighted significant exposure and vulnerability of the road network to fault displacement. Understanding fault displacement hazard and its impact on roads is crucial for mitigating risks and enhancing resilience. There is a need for regional-scale assessments of fault displacement to identify vulnerable areas within the road network for the purposes of planning and prioritising site-specific investigations. This thesis employs updated analysis of data from three historical surface-rupturing earthquakes (Edgecumbe 1987, Darfield 2010, and Kaikoūra 2016) to develop an empirical model that addresses the gap in regional fault displacement hazard analysis. The findings contribute to understanding of • How to use seismic hazard model inputs for regional fault displacement hazard analysis • How faulting type and sediment cover affects the magnitude and spatial distribution of fault displacement • How the distribution of displacement and regional fault displacement hazard is impacted by secondary faulting • The inherent uncertainties and limitations associated with employing an empirical approach at a regional scale • Which sections of New Zealand’s roading network are most susceptible to fault displacement hazard and warrant site-specific investigations • Which regions should prioritise updating emergency management plans to account for post-event disruptions to roading. I used displacement data from the aforementioned historical ruptures to generate displacement versus distance-to-fault curves for various displacement components, fault types, and geological characteristics. Using those relationships and established relationships for along-strike displacement, displacement contours were generated surrounding active faults within the NZ Community Fault Model. Next, I calculated a new measure of 1D strain along roads as well as relative hazard, which integrated 1D strain and normalised slip rate data. Summing these values at the regional level identified areas of heightened relative hazard across New Zealand, and permits an assessment of the susceptibility of road networks using geomorphon land classes as proxies for vulnerability. The results reveal that fault-parallel displacements tend to localise near the fault plane, while vertical and fault-perpendicular displacements sustain over extended distances. Notably, no significant disparities were observed in off-fault displacement between the hanging wall and footwall sides of the fault, or among different surface geology types, potentially attributed to dataset biases. The presence of secondary faulting in the dataset contributes to increased levels of tectonic displacement farther from the fault, highlighting its significance in hazard assessments. Furthermore, fault displacement contours delineate broader zones around dip-slip faults compared to strike-slip faults, with correlations identified between fault length and displacement width. Road ‘strain’ values are higher around dip-slip faults, with notable examples observed in the Westland and Buller Districts. As expected, relative hazard analysis revealed elevated values along faults with high slip rates, notably along the Alpine Fault. A regional-scale analysis of hazard and exposure reveals heightened relative hazard in specific regions, including Wellington, Southern Hawke’s Bay, Central Bay of Plenty, Central West Coast, inland Canterbury, and the Wairau Valley of Marlborough. Notably, the Central West Coast exhibits the highest summed relative hazard value, attributed to the fast-slipping Alpine Fault. The South Island generally experiences greater relative hazard due to larger and faster-slipping faults compared to the North Island, despite having fewer roads. Central regions of New Zealand face heightened risk compared to Southern or Northern regions. Critical road links intersecting high-slipping faults, such as State Highways 6, 73, 1, and 2, necessitate prioritisation for site-specific assessments, emergency management planning and targeted mitigation strategies. Roads intersecting with the Alpine Fault are prone to large parallel displacements, requiring post-quake repair efforts. Mitigation strategies include future road avoidance of nearby faults, modification of road fill and surface material, and acknowledgement of inherent risk, leading to prioritised repair efforts of critical roads post-quake. Implementing these strategies enhances emergency response efforts by improving accessibility to isolated regions following a major surface-rupturing event, facilitating faster supply delivery and evacuation assistance. This thesis contributes to the advancement of understanding fault displacement hazard by introducing a novel regional, empirical approach. The methods and findings highlight the importance of further developing such analyses and extending them to other critical infrastructure types exposed to fault displacement hazard in New Zealand. Enhancing our comprehension of the risks associated with fault displacement hazard offers valuable insights into various mitigation strategies for roading infrastructure and informs emergency response planning, thereby enhancing both national and global infrastructure resilience against geological hazards.
Fine grained sediment deposition in urban environments during natural hazard events can impact critical infrastructure and properties (urban terrain) leading to reduced social and economic function and potentially adverse public health effects. Therefore, clean-up of the sediments is required to minimise impacts and restore social and economic functionality as soon as possible. The strategies employed to manage and coordinate the clean-up significantly influence the speed, cost and quality of the clean-up operation. Additionally, the physical properties of the fine grained sediment affects the clean-up, transport, storage and future usage of the sediment. The goals of the research are to assess the resources, time and cost required for fine grained sediment clean-up in an urban environment following a disaster and to determine how the geotechnical properties of sediment will affect urban clean-up strategies. The thesis focuses on the impact of fine grained sediment (<1 mm) deposition from three liquefaction events during the Canterbury earthquake sequence (2010-2011) on residential suburbs and transport networks in Christchurch. It also presents how geotechnical properties of the material may affect clean-up strategies and methods by presenting geotechnical analysis of tephra material from the North Island of New Zealand. Finally, lessons for disaster response planning and decision making for clean-up of sediment in urban environments are presented. A series of semi-structured interviews of key stakeholders supported by relevant academic literature and media reports were used to record the clean-up operation coordination and management and to make a preliminary qualification of the Christchurch liquefaction ejecta clean-up (costs breakdown, time, volume, resources, coordination, planning and priorities). Further analysis of the costs and resources involved for better accuracy was required and so the analysis of Christchurch City Council road management database (RAMM) was done. In order to make a transition from general fine sediment clean-up to specific types of fine disaster sediment clean-up, adequate information about the material properties is required as they will define how the material will be handled, transported and stored. Laboratory analysis of young volcanic tephra from the New Zealand’s North Island was performed to identify their geotechnical properties (density, granulometry, plasticity, composition and angle of repose). The major findings of this research were that emergency planning and the use of the coordinated incident management system (CIMS) system during the emergency were important to facilitate rapid clean-up tasking, management of resources and ultimately recovery from widespread and voluminous liquefaction ejecta deposition in eastern Christchurch. A total estimated cost of approximately $NZ 40 million was calculated for the Christchurch City clean-up following the 2010-2011 Canterbury earthquake sequence with a partial cost of $NZ 12 million for the Southern part of the city, where up to 33% (418 km) of the road network was impacted by liquefaction ejecta and required clearing of the material following the 22 February 2011 earthquake. Over 500,000 tonnes of ejecta has been stockpiled at Burwood landfill for all three liquefaction inducing earthquake events. The average cost per kilometre for the event clean-up was $NZ 5,500/km (4 September 2010), $NZ 11,650/km (22 February 2011) and $NZ 11,185/km (13 June 2011). The duration of clean-up time of residential properties and the road network was approximately two to three months for each of the three liquefaction ejecta events; despite events volumes and spatial distribution of ejecta. Interviews and quantitative analysis of RAMM data revealed that the experience and knowledge gained from the Darfield earthquake (4 September 2010) clean-up increased the efficiency of the following Christchurch earthquake induced liquefaction ejecta clean-up events. Density, particle size, particle shape, clay content and moisture content, are the important geotechnical properties that need to be considered when planning for a clean-up method that incorporates collection, transport and disposal or storage. The geotechnical properties for the tephra samples were analysed to increase preparedness and reaction response of potentially affected North Island cities from possible product from the active volcanoes in their region. The geotechnical results from this study show that volcanic tephra could be used in road or construction material but the properties would have to be further investigated for a New Zealand context. Using fresh volcanic material in road, building or flood control construction requires good understanding of the material properties and precaution during design and construction to extra care, but if well planned, it can be economically beneficial.
Geologic phenomena produced by earthquake shaking, including rockfalls and liquefaction features, provide important information on the intensity and spatiotemporal distribution of earthquake ground motions. The study of rockfall and liquefaction features produced in contemporary well- instrumented earthquakes increases our knowledge of how natural and anthropogenic environments respond to earthquakes and improves our ability to deduce seismologic information from analogous pre-contemporary (paleo-) geologic features. The study of contemporary and paleo- rockfall and liquefaction features enables improved forecasting of environmental responses to future earthquakes. In this thesis I utilize a combination of field and imagery-based mapping, trenching, stratigraphy, and numerical dating techniques to understand the nature and timing of rockfalls (and hillslope sedimentation) and liquefaction in the eastern South Island of New Zealand, and to examine the influence that anthropogenic activity has had on the geologic expressions of earthquake phenomena. At Rapaki (Banks Peninsula, NZ), field and imagery-based mapping, statistical analysis and numerical modeling was conducted on rockfall boulders triggered by the fatal 2011 Christchurch earthquakes (n=285) and compared with newly identified prehistoric (Holocene and Pleistocene) boulders (n=1049) deposited on the same hillslope. A significant population of modern boulders (n=26) travelled farther downslope (>150 m) than their most-travelled prehistoric counterparts, causing extensive damage to residential dwellings at the foot of the hillslope. Replication of prehistoric boulder distributions using 3-dimensional rigid body numerical models requires the application of a drag-coefficient, attributed to moderate to dense slope vegetation, to account for their spatial distribution. Radiocarbon dating provides evidence for 17th to early 20th century deforestation at the study site during Polynesian and European colonization and after emplacement of prehistoric rockfalls. Anthropocene deforestation enabled modern rockfalls to exceed the limits of their prehistoric predecessors, highlighting a shift in the geologic expression of rockfalls due to anthropogenic activity. Optical and radiocarbon dating of loessic hillslope sediments in New Zealand’s South Island is used to constrain the timing of prehistoric rockfalls and associated seismic events, and quantify spatial and temporal patterns of hillslope sedimentation including responses to seismic and anthropogenic forcing. Luminescence ages from loessic sediments constrain timing of boulder emplacement to between ~3.0 and ~12.5 ka, well before the arrival of Polynesians (ca AD 1280) and Europeans (ca AD 1800) in New Zealand, and suggest loess accumulation was continuing at the study site until 12-13 ka. Large (>5 m3) prehistoric rockfall boulders preserve an important record of Holocene hillslope sedimentation by creating local traps for sediment aggradation and upbuilding soil formation. Sediment accumulation rates increased considerably (>~10 factor increase) following human arrival and associated anthropogenic burning of hillslope vegetation. New numerical ages are presented to place the evolution of loess-mantled hillslopes in New Zealand’s South Island into a longer temporal framework and highlight the roles of earthquakes and humans on hillslope surface process. Extensive field mapping and characterization for 1733 individual prehistoric rockfall boulders was conducted at Rapaki and another Banks Peninsula site, Purau, to understand their origin, frequency, and spatial and volumetric distributions. Boulder characteristics and distributions were compared to 421 boulders deposited at the same sites during the 2010-2011 Canterbury earthquake sequence. Prehistoric boulders at Rapaki and Purau are comprised of two dominant lithofacies types: volcanic breccia and massive (coherent) lava basalt. Volcanic breccia boulders are found in greatest abundance (64-73% of total mapped rockfall) and volume (~90-96% of total rockfall) at both locations and exclusively comprise the largest boulders with the longest runout distances that pose the greatest hazard to life and property. This study highlights the primary influence that volcanic lithofacies architecture has on rockfall hazard. The influence of anthropogenic modifications on the surface and subsurface geologic expression of contemporary liquefaction created during the 2010-2011 Canterbury earthquake sequence (CES) in eastern Christchurch is examined. Trench observations indicate that anthropogenic fill layer boundaries and the composition/texture of discretely placed fill layers play an important role in absorbing fluidized sand/silt and controlling the subsurface architecture of preserved liquefaction features. Surface liquefaction morphologies (i.e. sand blows and linear sand blow arrays) display alignment with existing utility lines and utility excavations (and perforated pipes) provided conduits for liquefaction ejecta during the CES. No evidence of pre-CES liquefaction was identified within the anthropogenic fill layers or underlying native sediment. Radiocarbon dating of charcoal within the youngest native sediment suggests liquefaction has not occurred at the study site for at least the past 750-800 years. The importance of systematically examining the impact of buried infrastructure on channelizing and influencing surface and subsurface liquefaction morphologies is demonstrated. This thesis highlights the importance of using a multi-technique approach for understanding prehistoric and contemporary earthquake phenomena and emphasizes the critical role that humans play in shaping the geologic record and Earth’s surface processes.
As a consequence of the 2010 – 2011 Canterbury earthquake sequence, Christchurch experienced widespread liquefaction, vertical settlement and lateral spreading. These geological processes caused extensive damage to both housing and infrastructure, and increased the need for geotechnical investigation substantially. Cone Penetration Testing (CPT) has become the most common method for liquefaction assessment in Christchurch, and issues have been identified with the soil behaviour type, liquefaction potential and vertical settlement estimates, particularly in the north-western suburbs of Christchurch where soils consist mostly of silts, clayey silts and silty clays. The CPT soil behaviour type often appears to over-estimate the fines content within a soil, while the liquefaction potential and vertical settlement are often calculated higher than those measured after the Canterbury earthquake sequence. To investigate these issues, laboratory work was carried out on three adjacent CPT/borehole pairs from the Groynes Park subdivision in northern Christchurch. Boreholes were logged according to NZGS standards, separated into stratigraphic layers, and laboratory tests were conducted on representative samples. Comparison of these results with the CPT soil behaviour types provided valuable information, where 62% of soils on average were specified by the CPT at the Groynes Park subdivision as finer than what was actually present, 20% of soils on average were specified as coarser than what was actually present, and only 18% of soils on average were correctly classified by the CPT. Hence the CPT soil behaviour type is not accurately describing the stratigraphic profile at the Groynes Park subdivision, and it is understood that this is also the case in much of northwest Christchurch where similar soils are found. The computer software CLiq, by GeoLogismiki, uses assessment parameter constants which are able to be adjusted with each CPT file, in an attempt to make each more accurate. These parameter changes can in some cases substantially alter the results for liquefaction analysis. The sensitivity of the overall assessment method, raising and lowering the water table, lowering the soil behaviour type index, Ic, liquefaction cutoff value, the layer detection option, and the weighting factor option, were analysed by comparison with a set of ‘base settings’. The investigation confirmed that liquefaction analysis results can be very sensitive to the parameters selected, and demonstrated the dependency of the soil behaviour type on the soil behaviour type index, as the tested assessment parameters made very little to no changes to the soil behaviour type plots. The soil behaviour type index, Ic, developed by Robertson and Wride (1998) has been used to define a soil’s behaviour type, which is defined according to a set of numerical boundaries. In addition to this, the liquefaction cutoff point is defined as Ic > 2.6, whereby it is assumed that any soils with an Ic value above this will not liquefy due to clay-like tendencies (Robertson and Wride, 1998). The method has been identified in this thesis as being potentially unsuitable for some areas of Christchurch as it was developed for mostly sandy soils. An alternative methodology involving adjustment of the Robertson and Wride (1998) soil behaviour type boundaries is proposed as follows: Ic < 1.31 – Gravelly sand to dense sand 1.31 < Ic < 1.90 – Sands: clean sand to silty sand 1.90 < Ic < 2.50 – Sand mixtures: silty sand to sandy silt 2.50 < Ic < 3.20 – Silt mixtures: clayey silt to silty clay 3.20 < Ic < 3.60 – Clays: silty clay to clay Ic > 3.60 – Organics soils: peats. When the soil behaviour type boundary changes were applied to 15 test sites throughout Christchurch, 67% showed an improved change of soil behaviour type, while the remaining 33% remained unchanged, because they consisted almost entirely of sand. Within these boundary changes, the liquefaction cutoff point was moved from Ic > 2.6 to Ic > 2.5 and altered the liquefaction potential and vertical settlement to more realistic ii values. This confirmed that the overall soil behaviour type boundary changes appear to solve both the soil behaviour type issues and reduce the overestimation of liquefaction potential and vertical settlement. This thesis acts as a starting point towards researching the issues discussed. In particular, future work which would be useful includes investigation of the CLiq assessment parameter adjustments, and those which would be most suitable for use in clay-rich soils such as those in Christchurch. In particular consideration of how the water table can be better assessed when perched layers of water exist, with the limitation that only one elevation can be entered into CLiq. Additionally, a useful investigation would be a comparison of the known liquefaction and settlements from the Canterbury earthquake sequence with the liquefaction and settlement potentials calculated in CLiq for equivalent shaking conditions. This would enable the difference between the two to be accurately defined, and a suitable adjustment applied. Finally, inconsistencies between the Laser-Sizer and Hydrometer should be investigated, as the Laser-Sizer under-estimated the fines content by up to one third of the Hydrometer values.
In 2010 and 2011 Christchurch, New Zealand experienced a series of earthquakes that caused extensive damage across the city, but primarily to the Central Business District (CBD) and eastern suburbs. A major feature of the observed damage was extensive and severe soil liquefaction and associated ground damage, affecting buildings and infrastructure. The behaviour of soil during earthquake loading is a complex phenomena that can be most comprehensively analysed through advanced numerical simulations to aid engineers in the design of important buildings and critical facilities. These numerical simulations are highly dependent on the capabilities of the constitutive soil model to replicate the salient features of sand behaviour during cyclic loading, including liquefaction and cyclic mobility, such as the Stress-Density model. For robust analyses advanced soil models require extensive testing to derive engineering parameters under varying loading conditions for calibration. Prior to this research project little testing on Christchurch sands had been completed, and none from natural samples containing important features such as fabric and structure of the sand that may be influenced by the unique stress-history of the deposit. This research programme is focussed on the characterisation of Christchurch sands, as typically found in the CBD, to facilitate advanced soil modelling in both res earch and engineering practice - to simulate earthquake loading on proposed foundation design solutions including expensive ground improvement treatments. This has involved the use of a new Gel Push (GP) sampler to obtain undisturbed samples from below the ground-water table. Due to the variable nature of fluvial deposition, samples with a wide range of soil gradations, and accordingly soil index properties, were obtained from the sampling sites. The quality of the samples is comprehensively examined using available data from the ground investigation and laboratory testing. A meta-quality assessment was considered whereby a each method of evaluation contributed to the final quality index assigned to the specimen. The sampling sites were characterised with available geotechnical field-based test data, primarily the Cone Penetrometer Test (CPT), supported by borehole sampling and shear-wave velocity testing. This characterisation provides a geo- logical context to the sampling sites and samples obtained for element testing. It also facilitated the evaluation of sample quality. The sampling sites were evaluated for liquefaction hazard using the industry standard empirical procedures, and showed good correlation to observations made following the 22 February 2011 earthquake. However, the empirical method over-predicted liquefaction occurrence during the preceding 4 September 2010 event, and under-predicted for the subsequent 13 June 2011 event. The reasons for these discrepancies are discussed. The response of the GP samples to monotonic and cyclic loading was measured in the laboratory through triaxial testing at the University of Canterbury geomechanics laboratory. The undisturbed samples were compared to reconstituted specimens formed in the lab in an attempt to quantify the effect of fabric and structure in the Christchurch sands. Further testing of moist tamped re- constituted specimens (MT) was conducted to define important state parameters and state-dependent properties including the Critical State Line (CSL), and the stress-strain curve for varying state index. To account for the wide-ranging soil gradations, selected representative specimens were used to define four distinct CSL. The input parameters for the Stress-Density Model (S-D) were derived from a suite of tests performed on each representative soil, and with reference to available GP sample data. The results of testing were scrutinised by comparing the data against expected trends. The influence of fabric and structure of the GP samples was observed to result in similar cyclic strength curves at 5 % Double Amplitude (DA) strain criteria, however on close inspection of the test data, clear differences emerged. The natural samples exhibited higher compressibility during initial loading cycles, but thereafter typically exhibited steady growth of plastic strain and excess pore water pressure towards and beyond the strain criteria and initial liquefaction, and no flow was observed. By contrast the reconstituted specimens exhibited a stiffer response during initial loading cycles, but exponential growth in strains and associated excess pore water pressure beyond phase-transformation, and particularly after initial liquefaction where large strains were mobilised in subsequent cycles. These behavioural differences were not well characterised by the cyclic strength curve at 5 % DA strain level, which showed a similar strength for both GP samples and MT specimens. A preliminary calibration of the S-D model for a range of soil gradations is derived from the suite of laboratory test data. Issues encountered include the influence of natural structure on the peak-strength–state index relationship, resulting in much higher peak strengths than typically observed for sands in the literature. For the S-D model this resulted in excessive stiffness to be modelled during cyclic mobility, when the state index becomes large momentarily, causing strain development to halt. This behaviour prevented modelling the observed re- sponse of silty sands to large strains, synonymous with “liquefaction”. Efforts to reduce this effect within the current formulation are proposed as well as future research to address this issue.
One of the less understood geotechnical responses to the cyclic loading from the MW6.2 Christchurch Earthquake, on the 22nd of February 2011, is the fissuring in the loessial soil-mantled, footslope positions of the north-facing valleys of the Port Hills. The fissures are characterized by mostly horizontal offset (≤500mm), with minor vertical displacement (≤300mm), and they extend along both sides of valleys for several hundred metres in an approximately contour-parallel orientation. The fissure traces correspond to extensional features mapped in other studies. Previous studies have suggested that the fissures are the headscarps of incipient landslides, but the surface and subsurface features are not typical of landslide movement. Whilst there are some features that correlate with landslide movement, there are many features that contradict the landslide movement hypothesis. Of critical importance to this investigation was the fact that there are no landslide flanks, there has been no basal shear surface found, there is little deformation in the so-called ‘landslide body’, and there have been no recorded zones of low shear strength in the soil deposit that are indicative of a basal shear surface. This thesis is a detailed geotechnical study on the fissures along part of Ramahana Road in the Hillsborough Valley, Christchurch. Shallow and deep investigation methods found that the predominant soil is loess-colluvium, to depths of ~20m, and this soil has variable geotechnical characteristics depending on the layer sampled. The factor that has the most influence on shear strength was found to be the moisture content. Direct shear-box testing of disturbed, recompacted loess-colluvium found that the soil had a cohesion of 35-65kPa and a friction angle of 38-43° when the soil moisture content was at 8-10%. However when the moisture content was at 19-20% the soil’s cohesion decreased to 3-5kPa and its friction angle decreased to 33-38°, this moisture content is at or slightly above the plastic limit. An electrical resistivity geophysical survey was conducted perpendicular to multiple fissure traces and through the compressional zone at 17 Ramahana Road. The electrical resistivity line found that there was an area of high resistivity at the toe of the slope, and an area of high conductivity downslope of this and at greater depths. This area correlated to the compressional zone recorded by previous studies. Moisture content testing of the soil in these locations showed that the soil in the resistive area was relatively dry (9%) compared to the surrounding soil (13%), whilst the soil in the conductive area was relatively wet (22%)compared to the surrounding soil (19%). Density tests of the soil in the compressional zone recorded that the resistive area had a higher dry density than the surrounding soil (~1790 kg/m3 compared to ~1650 kg/m3). New springs arose downslope of the compressional zone contemporaneously with the fissures, and it is interpreted that these have arisen from increased hydraulic head in the Banks Peninsula bedrock aquifer system, and earthquake induced-bedrock fracturing. A test pit was dug across an infilled fissure trace at 17 Ramahana Road to a depth of 3m. The fissure trace had an aperture of 450-470mm at the ground surface, but it gradually lost aperture with depth until 2.0-2.1m where it became a segmented fissure trace with 1-2mm aperture. A mixed-colluvium layer was intercepted by the fissure trace at 2.4m depth, and there was no observable vertical offset of this layer. The fissure trace was at an angle of 78° at the ground surface, but it also flattened with depth, which gave it a slightly curved appearance. The fissure trace was at an assumed angle of 40-50° near the base of the test pit. Rotational slide, translational slide and lateral spread landslide movement types were compared and contrasted as possibilities for landslide movement types, whilst an alternative hypothesis was offered that the fissures are tensile failures with a quasi-toppling motion involving a cohesive block of loessial soil moving outwards from the slope, with an accommodating compressional strain in the lower less cohesive soil. The mechanisms behind this movement are suggested to be the horizontal earthquake inertia forces from the Christchurch Earthquake, the static shear stress of the slope, and bedrock uplift of the Port Hills in relation to the subsidence of the Christchurch city flatlands. Extremely high PGA is considered to be a prerequisite to the fissure trace development, and these can only be induced in the Hillsborough Valley from a Port Hills Fault rupture, which has a recurrence interval of ~10,000 years. The current understanding of how the loess-colluvium soil would behave under cyclic loading is limited, and the mechanisms behind the suggested movement type are not completely understood. Further research is needed to confirm the proposed mechanism of the fissure traces. Laboratory tests such as the cyclic triaxial and cyclic shear test would be beneficial in future research to quantitatively test how the soil behaves under cyclic loading at various moisture contents and clay contents, and centrifuge experiments would be of great use to qualitatively test the suggested mode of movement in the loessial soil.
This project was initiated by ENGEO Limited and KiwiRail Holdings Limited to assess the stability of Slovens Creek Viaduct (specifically its western abutment) and a 3km section of rail corridor between Slovens Creek Viaduct and Avoca on the Midland Line (MDL). Commonly known as the scenic TranzAlpine rail journey (through Arthurs Pass National Park) the MDL connects Greymouth to Christchurch via Rolleston, where the MDL meets the Main South Line into Christchurch. The project area is approximately 40km southeast of Arthurs Pass Township, in the eastern extension of the Castle Hill Basin which is part of the Waimakariri Catchment and Canterbury Foothills. The field area is underlain by Rakaia Terrane, which is part of the Torlesse Composite Terrane forming the basement rock unit for the field area. Cretaceous-Tertiary rocks of the Castle Hill Basin overlie the basement strata and record a transgression-regression sequence, as well as mid-Oligocene submarine volcanism. The stratigraphic sequence in the Castle Hill Basin, and its eastern extension to Avoca, comprises two formations of the Eyre group, the older Broken River Formation and the younger Iron Creek Formation. Deep marine Porter Group limestones, marls, and tuffs of Oligocene age succeed the Iron Creek Formation of the Eyre Group, and probably records the maximum of the transgression. The Enys Formation lies disconformably on the Porter Group and is overlain unconformably by Late Pleistocene glacifluvial and glacial deposits. The Tertiary strata in the Slovens-Avoca rail corridor are weak, and the clay-rich tuff derived from mid-Oligocene volcanism is particularly prone to slaking. Extensive mapping carried out for this project has identified that some 90 percent of the surface along the length of the Slovens-Avoca corridor has been subject to mass movement. The landslides of the Slovens-Avoca rail corridor are clearly younger than the Last Glaciation, and Slovens Creek has been downcutting, with associated faulting and uplift, to form the present day geomorphology of the rail corridor. Deep-seated landslides in the rail corridor extend to Slovens Creek, locally deflecting the stream course, and a generic ground failure model for the rail corridor has been developed. Exploratory geotechnical investigations, including core drilling, installation of an inclinometer and a piezometer, enabled the construction of a simple ground model and cross section for the Slovens Creek Viaduct western abutment. Limit-equilibrium and pseudo-static slope stability analyses using both circular and block critical slip surface search methods were applied to the ground model for the western abutment of Slovens Creek Viaduct. Piezometric and strength data obtained during laboratory testing of core material have been used to constrain the western abutment stability assessment for one representative section line (C-C’). Prior to pseudo-static sensitivity analyses peak ground acceleration (PGA) for various Ultimate Limit State (ULS) design return periods, defined by an equation given in NZS1170.5:2004, were calculated and have been used as a calibration technique to find and compare specific PGA values for pseudo-static analyses in the Slovens Creek Viaduct area. The main purpose has been to provide an indication of how railway infrastructure could be affected by seismic events of various return periods defined by ULS design standards for the area. Limit equilibrium circular slip surface search methods, both grid search and auto refine search, indicated the slope is stable with a FoS greater than 1.0 returned from each, although one particular surface returned the lowest FoS in each. This surface is in the lower portion of the slope, adjacent to Slovens Stream and northeast of the MDL. As expected, pseudo-static analyses returned a lower FoS overall when compared to limit equilibrium analyses. The PGA analyses suggest that partial ground failure at the Slovens Creek Viaduct western abutment could occur in a 1 in 25-year return period event within materials on the slower slope beyond the immediate rail corridor. A ULS (1 in 500-year) event in the Slovens Creek Viaduct area would likely produce a PGA of ~0.9g, and the effects on the western abutment and rail infrastructure would most likely be catastrophic. Observed ground conditions for the western abutment of the Slovens Creek Viaduct suggest there is no movement within the landslide at depth within the monitoring timeframe of this project (22 May 2015 – 4 August 2015). Slope stability monitoring is recommended to be continued in two parts: (1) the inclinometer in BH1 is to be monitored on a six monthly basis for one year following completion of this thesis, and then annually unless ground movements become evident; and (2) surface movement monitoring should be installed using a fixed datum on the stable eastern abutment. Long-term stability management strategies for the Slovens Creek Viaduct western abutment are dependent upon future observed changes and ongoing monitoring. Hazard and risk assessment using the KiwiRail Qualitative Risk Assessment Framework (QRA) is recommended, and if slope stability becomes problematic for operation of the Midland Line consideration should be given to deep slope drainage. In the event of a large magnitude or high PGA earthquake all monitoring should be reviewed.
Background The 2010/2011 Canterbury earthquakes and aftershocks in New Zealand caused unprecedented destruction to the physical, social, economic, and community fabric of Christchurch city. The recovery phase in Christchurch is on going, six years following the initial earthquake. Research exploring how disabled populations experience community inclusion in the longer-term recovery following natural disasters is scant. Yet such information is vital to ensure that recovering communities are inclusive for all members of the affected population. This thesis specifically examined how people who use wheelchairs experienced community inclusion four years following the 2010/2011 Canterbury earthquakes. Aims The primary research aim was to understand how one section of the disability community – people who use wheelchairs – experienced community inclusion over the four years following the 2010/2011 Canterbury earthquakes and aftershocks. A secondary aim was to test a novel sampling approach, Respondent Driven Sampling, which had the potential to enable unbiased population-based estimates. This was motivated by the lack of an available sampling frame for the target population, which would inhibit recruitment of a representative sample. Methodology and methods An exploratory sequential mixed methods design was used, beginning with a qualitative phase (Phase One), which informed a second quantitative phase (Phase Two). The qualitative phase had two stages. First, a small sample of people who use wheelchairs participated in an individual, semi-structured interview. In the second stage, these participants were then invited to a group interview to clarify and prioritise themes identified in the individual interviews. The quantitative phase was a cross-sectional survey developed from the findings from Phase One. Initially, Respondent Driven Sampling was employed to conduct a national, electronic cross-sectional survey that aimed to recruit a sample that may provide unbiased population-based estimates. Following the unsuccessful application of Respondent Driven Sampling, a region-specific convenience sampling approach was used. The datasets from the qualitative and quantitative phases were integrated to address the primary aim of the research. Results In Phase One 13 participants completed the individual interviews, and five of them contributed to the group interview. Thematic analysis of individual and group interview data suggested that participants felt the 2010/11 earthquakes magnified many pre-existing barriers to community inclusion, and also created an exciting opportunity for change. This finding was encapsulated in five themes: 1) earthquakes magnified barriers, 2) community inclusion requires energy, 3) social connections are important, 4) an opportunity lost, and 5) an opportunity found. The findings from Phase One informed the development of a survey instrument to investigate how these findings generalised to a larger sample of individuals who use wheelchairs. In Phase Two, the Respondent Driven Sampling approach failed to recruit enough participants to satisfy the statistical requirements needed to reach equilibrium, thereby enabling the calculation of unbiased population estimates. The subsequent convenience sampling approach recruited 49 participants who, combined with the 15 participants from the Respondent Driven Sampling approach that remained eligible for the region-specific sample, resulted in the total of 64 individuals who used wheelchairs and were residents of Christchurch. Participants reported their level of community inclusion at three time periods: the six months prior to the first earthquake in September 2010 (time one), the six months following the first earthquake in September 2010 (time two), and the six months prior to survey completion (between October 2015 and March 2016, (time three)). Survey data provided some precision regarding the timing in which the magnified barriers developed. Difficulty with community inclusion rose significantly between time one and time two, and while reducing slightly, was still present during time three, and had not returned to the time one baseline. The integrated findings from Phase One and Phase Two suggested that magnified barriers to community inclusion had been sustained four years post-earthquake, and community access had not returned to pre-earthquake levels, let alone improved beyond pre-earthquake levels. Conclusion Findings from this mixed methods study suggest that four years following the initial earthquake, participants were still experiencing multiple magnified barriers, which contributed to physical and social exclusion, as well as fatigue, as participants relied on individual agency to negotiate such barriers. Participants also highlighted the exciting opportunity to create an accessible city. However because they were still experiencing barriers four years following the initial event, and were concerned that this opportunity might be lost if the recovery proceeds without commitment and awareness from the numerous stakeholders involved in guiding the recovery. To truly realise the opportunity to create an accessible city following a disaster, the transition from the response phase to a sustainable longer-term recovery must adopt a new model of community engagement where decision-makers partner with people living with disability to co-produce a vision and strategy for creating an inclusive community. Furthermore, despite the unsuccessful use of Respondent Driven Sampling in this study, future research exploring the application of RDS with wheelchair users is recommended before discounting this sampling approach in this population.
