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Images for 2011 Christchurch earthquake; more images...

Research papers, University of Canterbury Library

The 2010-2011 Canterbury earthquake sequence was extremely damaging to structures in Christchurch and continues to have a large economic and social impact on the city and surrounding regions. In addition to strong ground shaking (Bradley and Cubrinovski 2011 SRL; Bradley 2012 SDEE), extensive liquefaction was observed, particularly in the 4 September 2010 Darfield earthquake and the 22 February 2011 Christchurch earthquake (Cubrinovski et al. 2010 BNZSEE; 2011 SRL). Large observed vertical ground motion amplitudes were recorded in the events in this sequence, with vertical peak ground accelerations of over 2.2g being observed at the Heathcote Valley Primary School during the Christchurch earthquake, and numerous other vertical motions exceeding 1.0g (Bradley and Cubrinovski 2011 SRL; Bradley 2012 SDEE; Fry et al 2011 SRL). Vertical peak ground accelerations of over 1.2g were observed in the Darfield earthquake.

Audio, Radio New Zealand

Former Christchurch restaurateur James Jameson ran a cafe in the Christchurch Arts Centre until the Canterbury earthquakes of 2011. Last year, James moved to Mt Lyford – the area hit hard and isolated by this month's earthquakes.

Videos, UC QuakeStudies

A video of the 2016 Civic Earthquake Memorial Service, held to mark the fifth anniversary of the 22 February 2011 earthquake. The service was held on the Archery Lawn in the Christchurch Botanic Gardens at midday on 22 February 2016. The service was filmed for the Christchurch City Council by Alan Radford of Multicam TV.

Articles, Christchurch uncovered

As life-changing experiences go, the earthquake on 22 February 2011 was fairly significant. On the one hand, our house was red-zoned (but still liveable), friends lost their lives and the city lost many of the old buildings that, for me, … Continue reading →

Images, eqnz.chch.2010

Pigeons sit on the remains of one of the tallest buildings in Christchurch that was 95% demolished two or three years ago. The basement (now filled with water) and the columns remain. Demolished due to damage from the Christchurch 2011 earthquake.

Research papers, University of Canterbury Library

Liquefaction-induced lateral spreading in large seismic events often results in pervasive and costly damage to engineering structures and lifelines, making it a critical component of engineering design. However, the complex nature of this phenomenon leads to designing for such a hazard extremely challenging and there is a clear for an improved understanding and predicting liquefaction-induced lateral spreading. The 2010-2011 Canterbury (New Zealand) Earthquakes triggered severe liquefaction-induced lateral spreading along the streams and rivers of the Christchurch region, causing extensive damage to roads, bridges, lifelines, and structures in the vicinity. The unfortunate devastation induced from lateral spreading in these events also rendered the rare opportunity to gain an improved understanding of lateral spreading displacements specific to the Christchurch region. As part of this thesis, the method of ground surveying was employed following the 4 September 2010 Darfield (Mw 7.1) and 22 February 2011 Christchurch (Mw 6.2) earthquakes at 126 locations (19 repeated) throughout Christchurch and surrounding suburbs. The method involved measurements and then summation of crack widths along a specific alignment (transect) running approximately perpendicular to the waterway to indicate typically a maximum lateral displacement at the bank and reduction of the magnitude of displacements with distance from the river. Rigorous data processing and comparisons with alternative measurements of lateral spreading were performed to verify results from field observations and validate the method of ground surveying employed, as well as highlight the complex nature of lateral spreading displacements. The welldocumented field data was scrutinized to gain an understanding of typical magnitudes and distribution patterns (distribution of displacement with distance) of lateral spreading observed in the Christchurch area. Maximum displacements ranging from less than 10 cm to over 3.5 m were encountered at the sites surveyed and the area affected by spreading ranged from less than 20 m to over 200 m from the river. Despite the highly non-uniform displacements, four characteristic distribution patterns including large, distributed ground displacements, block-type movements, large and localized ground displacements, and areas of little to no displacements were identified. Available geotechnical, seismic, and topographic data were collated at the ground surveying sites for subsequent analysis of field measurements. Two widely-used empirical models (Zhang et al. (2004), Youd et al. (2002)) were scrutinized and applied to locations in the vicinity of field measurements for comparison with model predictions. The results indicated generally poor correlation (outside a factor of two) with empirical predictions at most locations and further validated the need for an improved, analysis- based method of predicting lateral displacements that considers the many factors involved on a site-specific basis. In addition, the development of appropriate model input parameters for the Youd et al. (2002) model led to a site-specific correlation of soil behavior type index, Ic, and fines content, FC, for sites along the Avon River in Christchurch that matched up well with existing Ic – FC relationships commonly used in current practice. Lastly, a rigorous analysis was performed for 25 selected locations of ground surveying measurements along the Avon River where ground slope conditions are mild (-1 to 2%) and channel heights range from about 2 – 4.5 m. The field data was divided into categories based on the observed distribution pattern of ground displacements including: large and distributed, moderate and distributed, small to negligible, and large and localized. A systematic approach was applied to determine potential critical layers contributing to the observed displacement patterns which led to the development of characteristic profiles for each category considered. The results of these analyses outline an alternative approach to the evaluation of lateral spreading in which a detailed geotechnical analysis is used to identify the potential for large spreading displacements and likely spatial distribution patterns of spreading. Key factors affecting the observed magnitude and distribution of spreading included the thickness of the critical layer, relative density, soil type and layer continuity. It was found that the large and distributed ground displacements were associated with a thick (1.5 – 2.5 m) deposit of loose, fine to silty sand (qc1 ~4-7 MPa, Ic 1.9-2.1, qc1n_cs ~50-70) that was continuous along the bank and with distance from the river. In contrast, small to negligible displacements were characterized by an absence of or relatively thin (< 1 m), discontinuous critical layer. Characteristic features of the moderate and distributed displacements were found to be somewhere between these two extremes. The localized and large displacements showed a characteristic critical layer similar to that observed in the large and distributed sites but that was not continuous and hence leading to the localized zone of displacement. The findings presented in this thesis illustrate the highly complex nature of lateral displacements that cannot be captured in simplified models but require a robust geotechnical analysis similar to that performed for this research.

Videos, UC QuakeStudies

A video of a presentation by Professor David Johnston during the fourth plenary of the 2016 People in Disasters Conference. Johnston is a Senior Scientist at GNS Science and Director of the Joint Centre for Disaster Research in the School of Psychology at Massey University. The presentation is titled, "Understanding Immediate Human Behaviour to the 2010-2011 Canterbury Earthquake Sequence, Implications for injury prevention and risk communication".The abstract for the presentation reads as follows: The 2010 and 2011 Canterbury earthquake sequences have given us a unique opportunity to better understand human behaviour during and immediately after an earthquake. On 4 September 2010, a magnitude 7.1 earthquake occurred near Darfield in the Canterbury region of New Zealand. There were no deaths, but several thousand people sustained injuries and sought medical assistance. Less than 6 months later, a magnitude 6.2 earthquake occurred under Christchurch City at 12:51 p.m. on 22 February 2011. A total of 182 people were killed in the first 24 hours and over 7,000 people injured overall. To reduce earthquake casualties in future events, it is important to understand how people behaved during and immediately after the shaking, and how their behaviour exposed them to risk of death or injury. Most previous studies have relied on an analysis of medical records and/or reflective interviews and questionnaire studies. In Canterbury we were able to combine a range of methods to explore earthquake shaking behaviours and the causes of injuries. In New Zealand, the Accident Compensation Corporation (a national health payment scheme run by the government) allowed researchers to access injury data from over 9,500 people from the Darfield (4 September 2010) and Christchurch (22 February 2011 ) earthquakes. The total injury burden was analysed for demography, context of injury, causes of injury, and injury type. From the injury data inferences into human behaviour were derived. We were able to classify the injury context as direct (immediate shaking of the primary earthquake or aftershocks causing unavoidable injuries), and secondary (cause of injury after shaking ceased). A second study examined people's immediate responses to earthquakes in Christchurch New Zealand and compared responses to the 2011 earthquake in Hitachi, Japan. A further study has developed a systematic process and coding scheme to analyse earthquake video footage of human behaviour during strong earthquake shaking. From these studies a number of recommendations for injury prevention and risk communication can be made. In general, improved building codes, strengthening buildings, and securing fittings will reduce future earthquake deaths and injuries. However, the high rate of injuries incurred from undertaking an inappropriate action (e.g. moving around) during or immediately after an earthquake suggests that further education is needed to promote appropriate actions during and after earthquakes. In New Zealand - as in US and worldwide - public education efforts such as the 'Shakeout' exercise are trying to address the behavioural aspects of injury prevention.

Videos, UC QuakeStudies

A video of a presentation by Garry Williams during the fourth plenary of the 2016 People in Disasters Conference. Williams is the Programme Manager of the Ministry of Education's Greater Christchurch Education Renewal Programme. The presentation is titled, "Education Renewal: A section response to the February 2011 Christchurch earthquake".The abstract for this presentation reads as follows: The Canterbury earthquakes caused a disaster recovery situation unparalleled in New Zealand's history. In addition to widespread damage to residential dwellings and destruction of Christchurch's central business district, the earthquakes damaged more than 200 schools from Hurunui in the north, to the Mackenzie District in the east, and Timaru in the south. The impact on education provision was substantial, with the majority of early childhood centres, schools and tertiary providers experiencing damage or subsequent, with the majority of early childhood centres, schools and tertiary providers experiencing damage or subsequent operational issues caused by the ensuing migration of people. Following the February earthquake, over 12,000 students had left the school they had been attending and enrolled elsewhere - often at a school outside the region. Shortened school days and compression of teaching into short periods meant shift-sharing students engaged in the curriculum being delivered in more diverse ways. School principals and staff reported increased fatigue and stress and changes in student behaviours, often related to repeated exposure to and ongoing reminders of the trauma of the earthquakes. While there has been a shift from direct, trauma-related presentations to the indirect effects of psychological adversity and daily life stresses, international experiences tells us that psychological recovery generally lags behind the immediate physical recovery and rebuilding. The Ministries of Health and Education and the Canterbury District Health Board have developed and implemented a joint action plan to address specifically the emerging mental health issues for youth in Canterbury. However, the impact of vulnerable and stressed adults on children's behaviour contributes to the overall impact of ongoing wellbeing issues on the educational outcomes for the community. There is substantial evidence supporting the need to focus on adults' resilience so they can support children and youth. Much of the Ministry's work around supporting children under stress is through supporting the adults responsible for teaching them and leading their schools. The education renewal programme exists to assist education communities to rebuild and look toward renewal. The response to the earthquakes provides a significant opportunity to better meet the needs and aspirations of children and youth people. All the parents want to see their children eager to learn, achieving success, and gaining knowledge and skills that will, in time, enable them to become confident, adaptable, economically independent adults. But this is not always the case, hence our approach to education renewal seeks to address inequities and improve outcome, while prioritising actions that will have a positive impact on learners in greatest need of assistance.

Research papers, The University of Auckland Library

Many large-scale earthquakes all over the world have highlighted the impact of soil liquefaction to the built environment, but the scale of liquefaction-induced damage experienced in Christchurch and surrounding areas following the 2010-2011 Canterbury earthquake sequence (CES) was unparalleled, especially in terms of impact to an urban area. The short time interval between the large earthquakes presented a very rare occasion to examine liquefaction mechanism in natural deposits. The re-liquefaction experienced by the city highlighted the high liquefaction susceptibility of soil deposits in Christchurch, and presented a very challenging problem not only to the local residents but to the geotechnical engineering profession. This paper summarises the lessons learned from CES, and the impacts of the observations made to the current practice of liquefaction assessment and mitigation.

Research papers, Victoria University of Wellington

We examine the role of business interruption insurance in business recovery following the Christchurch earthquake in 2011 in the short- and medium-term. In the short-term analysis, we ask whether insurance increases the likelihood of business survival in the aftermath of a disaster. We find only weak evidence that those firms that had incurred damage, but were covered by business interruption insurance, had higher likelihood of survival post-quake compared with those firms that did not have insurance. This absence of evidence may reflect the high degree of uncertainty in the months following the 2011 earthquake and the multiplicity of severe aftershocks. For the medium-term, our results show a more explicit role for insurance in the aftermath of a disaster. Firms with business interruption insurance have a higher probability of increasing productivity and improved performance following a catastrophe. Furthermore, our results show that those organisations that receive prompt and full payments of their claims have a better recovery, in terms of profitability and a subjective ‘”better off” measure’ than those that had protracted or inadequate claim payments (less than 80% of the claim paid within 2.5 years). Interestingly, the latter group does worse than those organisations that had damage but no insurance coverage. This analysis strongly indicates the importance not only of good insurance coverage, but of an insurance system that also delivers prompt claim payments. As a first paper attempting to empirically identify a causal effect of insurance on business recovery, we also emphasize some caveats to our analysis.

Research papers, University of Canterbury Library

Liquefaction-induced lateral spreading during earthquakes poses a significant hazard to the built environment, as observed in Christchurch during the 2010 to 2011 Canterbury Earthquake Sequence (CES). It is critical that geotechnical earthquake engineers are able to adequately predict both the spatial extent of lateral spreads and magnitudes of associated ground movements for design purposes. Published empirical and semi-empirical models for predicting lateral spread displacements have been shown to vary by a factor of <0.5 to >2 from those measured in parts of Christchurch during CES. Comprehensive post- CES lateral spreading studies have clearly indicated that the spatial distribution of the horizontal displacements and extent of lateral spreading along the Avon River in eastern Christchurch were strongly influenced by geologic, stratigraphic and topographic features.

Research Papers, Lincoln University

The Canterbury earthquakes that happened in 2010 and 2011 have attracted many migrant workers to the region to assist with the rebuilding effort. However, research on the impact of influx of migrants on the labour market outcomes of a local industry post-disaster is limited internationally and locally. The main objective of this study is to examine the impact of the Canterbury earthquakes on the changes in demographic composition and occupational structure for the local and foreign workers in the Greater Christchurch construction industry. Replicating the discrete dependent variable regression methods used in the study by Sisk and Bankston III (2014), this study also aimed to compare their findings on the impact of the influx of migrants on the New Orleans construction industry with outcomes in Greater Christchurch. Customised data from New Zealand Censuses 2006 and 2013 were used to represent the pre- and post-earthquake periods. This study found that the rebuild has provided opportunities for migrant workers to enter the Greater Christchurch construction industry. The increased presence of migrant construction workers did not displace the locals. In fact, the likelihoods for both locals’ and migrants’ participation in the industry improved post-earthquakes. The earthquakes also increased overall workers’ participation at the lowest end of the occupational structure. However, the earthquakes created few significant changes to the distribution of local and migrant workers at the various occupational levels in the industry. Local workers still dominated all occupational levels post-earthquakes. The aggregated education levels of the construction workers were higher post-earthquakes, particularly among the migrant workers. Overall, migrant workers in the Greater Christchurch construction industry were more diverse, more educated and participated in higher occupational levels than migrants assisting in the New Orleans rebuild, due possibly to differences in immigration policies between New Zealand and the United States of America.

Research papers, University of Canterbury Library

Heathcote Valley school strong motion station (HVSC) consistently recorded ground motions with higher intensities than nearby stations during the 2010-2011 Canterbury earthquakes. For example, as shown in Figure 1, for the 22 February 2011 Christchurch earthquake, peak ground acceleration at HVSC reached 1.4 g (horizontal) and 2 g (vertical), the largest ever recorded in New Zealand. Strong amplification of ground motions is expected at Heathcote Valley due to: 1) the high impedance contrast at the soil-rock interface, and 2) the interference of incident and surface waves within the valley. However, both conventional empirical ground motion prediction equations (GMPE) and the physics-based large scale ground motions simulations (with empirical site response) are ineffective in predicting such amplification due to their respective inherent limitations.

Images, eqnz.chch.2010

The Forsyth Barr building has stood silent and empty (except the occasional intruder and pigeons) since the February 2011 earthquake. It was sold "as is" and I understand that it is now going to be fitted out as a hotel. This is the building that had severe stairwell damage during the quake necessitating people being lowered via ropes etc on t...

Research papers, University of Canterbury Library

The 2010-2011 Canterbury Earthquakes brought devastation to the city of Christchurch and has irrevocably affected the lives of the city’s residents. Years after the conclusion of these earthquakes, Christchurch and its residents are well on the path to recovery. Crime has proven an ongoing topic of discussion throughout this period, with news reports of increased burglary and arson in areas left largely abandoned by earthquake damage, and a rise in violent crime in suburban areas of Christchurch. Following the body of research that has considered the reaction of crime to natural disasters, this research has sought to comprehensively examine and understand the effects that the Canterbury Earthquakes had on crime. Examining Christchurch-wide offending, crime rates fell over the study period (July 2008 to June 2013), with the exception of domestic violence. Aside from a momentary increase in burglary in the days immediately following the Christchurch Earthquake, crime rates (as of 2013) have remained largely below pre-earthquake levels. Using Dual Kernel Density Estimation Analysis, a distinct spatial change in pre-earthquake crime hotspots was observed. These changes included an enormous decrease in central city offences, a rise in burglary in the eastern suburbs, and an increase in assault in areas outside of the central city. Logistic regression analysis, using a time-compensated dependent variable, identified a number of statistically-significant relationships between per CAU crime rate change and factors measuring socio-demographic characteristics, community cohesion, and the severity of disaster effects. The significance of these findings was discussed using elements of Social Disorganisation Theory, Routine Activity Theory, and Strain Theory. Consistent with past findings, social order was largely maintained following the Canterbury Earthquakes, with suggestion that increased collective efficacy and therapeutic communities had a negative influence on crime in the post-earthquake period. Areas of increased burglary and assault were associated with large population decreases, suggesting a link with the dissolution of communities and the removal of their inherent informal guardianship. Though observed, the increase in domestic violence was not associated with most neighbourhood-level variables. Trends in crime after the Canterbury Earthquakes were largely consistent with past research, and the media’s portrayal.

Research papers, University of Canterbury Library

This thesis explores how social entrepreneurship develops following a crisis. A review of literature finds that despite more than 15 years of academic attention, a common definition of social entrepreneurship remains elusive, with the field lacking the unified framework to set it apart as a specialised field of study. There are a variety of different conceptualisations of how social entrepreneurship works, and what it aims to achieve. The New Zealand context for social entrepreneurship is explored, finding that it receives little attention from the government and education sectors, despite its enormous potential. A lack of readily available information on social entrepreneurship leads most studies to investigate it as a phenomenon, and given the unique context of this research, it follows suit. Following from several authors’ recommendations that social entrepreneurship be subjected to further exploration, this is an exploratory, inductive study. A multiple case study is used to explore how social entrepreneurship develops following a natural disaster, using the example of the February 2011 earthquake in Christchurch, New Zealand. With little existing theory in this research area, this method is used to provide interesting examples of how the natural disaster, recognised as a crisis, can lead to business formation. Findings revealed the crisis initially triggered an altruistic response from social entrepreneurs, leading them to develop newly highlighted opportunities that were related to fields in which they had existing skills and expertise. In the process of developing these opportunities, initial altruistic motivations faded, with a new focus on the pursuit of a social mission and aims for survival and growth. The social missions addressed broad issues, and while they did address the crisis to differing extents, they were not confined to addressing its consequences. A framework is presented to explain how social entrepreneurship functions, once triggered in response to crisis. This framework supports existing literature that depicts social entrepreneurship as a continuous process, and illustrates the effects of a crisis as the catalyst for social business formation. In the aftermath of a crisis, when resources are likely to be scarce, social entrepreneurs play a significant role in the recovery process and their contributions should be highly valued both by government and relevant disaster response bodies. Policies that support social entrepreneurs and their ventures should be considered in the same way as commercial ventures.

Research papers, The University of Auckland Library

The connections between walls of unreinforced masonry (URM) buildings and flexible timber diaphragms are critical building components that must perform adequately before desirable earthquake response of URM buildings may be achieved. Field observations made during the initial reconnaissance and the subsequent damage surveys of clay brick URM buildings following the 2010/2011 Canterbury, New Zealand, earthquakes revealed numerous cases where anchor connections joining masonry walls or parapets with roof or floor diaphragms appeared to have failed prematurely. These observations were more frequent for adhesive anchor connections than for through-bolt connections (i.e., anchorages having plates on the exterior facade of the masonry walls). Subsequently, an in-field test program was undertaken in an attempt to evaluate the performance of adhesive anchor connections between unreinforced clay brick URM walls and roof or floor diaphragm. The study consisted of a total of almost 400 anchor tests conducted in eleven existing URM buildings located in Christchurch, Whanganui and Auckland. Specific objectives of the study included the identification of failure modes of adhesive anchors in existing URM walls and the influence of the following variables on anchor load-displacement response: adhesive type, strength of the masonry materials (brick and mortar), anchor embedment depth, anchor rod diameter, overburden level, anchor rod type, quality of installation, and the use of metal mesh sleeves. In addition, the comparative performance of bent anchors (installed at an angle of minimum 22.5° to the perpendicular projection from the wall surface) and anchors positioned horizontally was investigated. Observations on the performance of wall-to-diaphragm connections in the 2010/2011 Canterbury earthquakes, a summary of the performed experimental program and test results, and a proposed pull-out capacity relationship for adhesive anchors installed into multi-leaf clay brick masonry are presented herein. AM - Accepted Manuscript

Research Papers, Lincoln University

Liquefaction features and the geologic environment in which they formed were carefully studied at two sites near Lincoln in southwest Christchurch. We undertook geomorphic mapping, excavated trenches, and obtained hand cores in areas with surficial evidence for liquefaction and areas where no surficial evidence for liquefaction was present at two sites (Hardwick and Marchand). The liquefaction features identified include (1) sand blows (singular and aligned along linear fissures), (2) blisters or injections of subhorizontal dikes into the topsoil, (3) dikes related to the blows and blisters, and (4) a collapse structure. The spatial distribution of these surface liquefaction features correlates strongly with the ridges of scroll bars in meander settings. In addition, we discovered paleoliquefaction features, including several dikes and a sand blow, in excavations at the sites of modern liquefaction. The paleoliquefaction event at the Hardwick site is dated at A.D. 908-1336, and the one at the Marchand site is dated at A.D. 1017-1840 (95% confidence intervals of probability density functions obtained by Bayesian analysis). If both events are the same, given proximity of the sites, the time of the event is A.D. 1019-1337. If they are not, the one at the Marchand site could have been much younger. Taking into account a preliminary liquefaction-triggering threshold of equivalent peak ground acceleration for an Mw 7.5 event (PGA7:5) of 0:07g, existing magnitude-bounded relations for paleoliquefaction, and the timing of the paleoearthquakes and the potential PGA7:5 estimated for regional faults, we propose that the Porters Pass fault, Alpine fault, or the subduction zone faults are the most likely sources that could have triggered liquefaction at the study sites. There are other nearby regional faults that may have been the source, but there is no paleoseismic data with which to make the temporal link.

Research papers, The University of Auckland Library

An UnReinforced clay brick Masonry (URM) chimney is composed of a cantilever URM appendage above a roofline and is considered one of the most earthquake prone non-structural compo¬nents within vintage URM and timber-framed buildings. Observations from past earthquakes including the 1992 Big Bear City earthquake, 1994 Northridge earthquake, 2001 Nisqually earthquake, 2010/2011 Canterbury earthquakes, 2012 Northern Italy earthquakes, and 2014 South Napa earthquake served repeatedly as a reminder of the hazard induced by URM chimneys. The observed failure types included several cases where the adopted retrofit techniques were not adequate to effectively secure chimneys dur¬ing the earthquake. Data collected during the 2010/2011 post-earthquake building assessments in Christchurch and insur¬ance claims are reported herein. Five full-scale solid clay brick URM chimneys which replicated the most encountered geometrical and construction characteristics were subjected to shake table testing. Two chim¬ney samples were representative of the as-built conditions, while three samples were retrofitted using two different configurations of Near-Surface-Mounted (NSM) Carbon-Fibre-Reinforced-Polymer (CFRP) strips and post-tensioning techniques. The adopted securing techniques allowed an increase in seismic acceleration capacity of more than five times for chimneys constructed with ultra-weak mortar and more than twice for chimneys built with weak mortar. http://www.16ibmac.com/

Research papers, Victoria University of Wellington

The last seven years have seen southern New Zealand a ected by several large and damaging earthquakes: the moment magnitude (MW) 7.8 Dusky Sound earthquake on 15 July 2009, the MW 7.1 Dar eld (Canterbury) earthquake on 4 September 2010, and most notably the MW 6.2 Christchurch earthquake on 22 February 2011 and the protracted aftershock sequence. In this thesis, we address the postseismic displacement produced by these earthquakes using methods of satellite-based geodetic measurement, known as Interferometric Synthetic Aperture Radar (InSAR) and Global Positioning System (GPS), and computational modelling.  We observe several ground displacement features in the Canterbury and Fiordland regions during three periods: 1) Following the Dusky Sound earthquake; 2) Following the Dar eld earthquake and prior to the Christchurch earthquake; and 3) Following the Christchurch earthquake until February 2015.  The ground displacement associated with postseismic motion following the Dusky Sound earthquake has been measured by continuous and campaign GPS data acquired in August 2009, in conjunction with Di erential Interferometric Synthetic Aperture Radar (DInSAR) observations. We use an afterslip model, estimated by temporal inversion of geodetic data, with combined viscoelastic rebound model to account for the observed spatio-temporal patterns of displacement. The two postseismic processes together induce a signi cant displacement corresponding to principal extensional and contractual strain rates of the order of 10⁻⁷ and 10⁻⁸ yr⁻¹ respectively, across most of the southern South Island.  We also analyse observed postseismic displacement following the Dusky Sound earthquake using a new inversion approach in order to describe afterslip in an elasticviscoelastic medium. We develop a mathematical framework, namely the "Iterative Decoupling of Afterslip and Viscoelastic rebound (IDAV)" method, with which to invert temporally dense and spatially sparse geodetic observations. We examine the IDAV method using both numerical and analytical simulations of Green's functions.  For the post-Dar eld time interval, postseismic signals are measured within approximately one month of the mainshock. The dataset used for the post-Dar eld displacement spans the region surrounding previously unrecognised faults that ruptured during the mainshock. Poroelastic rebound in a multi-layered half-space and dilatancy recovery at shallow depths provide a satisfactory t with the observations.  For the post-Christchurch interval, campaign GPS data acquired in February 2012 to February 2015 in four successive epochs and 66 TerraSAR-X (TSX) SAR acquisitions in descending orbits between March 2011 and May 2014 reveal approximately three years of postseismic displacement. We detect movement away from the satellite of ~ 3 mm/yr in Christchurch and a gradient of displacement of ~ 4 mm/yr across a lineament extending from the westernmost end of the Western Christchurch Fault towards the eastern end of the Greendale East Fault. The postseismic signals following the Christchurch earthquake are mainly accounted for by afterslip models on the subsurface lineament and nearby faults.