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Videos, UC QuakeStudies

A video of an interview with Allison Naylor about her property in the Flockton Basin. Naylor had to leave her house after flooding made it unliveable. This video was part of a series of videos about residents in the flood-prone Flockton Basin.

Videos, UC QuakeStudies

A video of an interview with Rose Lennon about her property in the Flockton Basin. Lennon's house has been damaged by flooding in the area. This video was part of a series of videos about residents in the flood-prone Flockton Basin.

Videos, UC QuakeStudies

A video of an interview with Pamela Wilkinson about her property in the Flockton Basin. Wilkinson had to leave her house after flooding made in unliveable. This video was part of a series of videos about residents in the flood-prone Flockton Basin.

Videos, UC QuakeStudies

A video of an interview with Jane Rooney about her property in the Flockton Basin. Rooney's house has been damaged by flooding in the area. This video was part of a series of videos about residents in the flood-prone Flockton Basin.

Videos, UC QuakeStudies

A video of an interview with Robyn Simpson about her property in the Flockton Basin. Simpson had to leave her house after flooding made in unliveable. This video was part of a series of videos about residents in the flood-prone Flockton Basin.

Videos, UC QuakeStudies

A video of an interview with Hamish Griffen and Leila Chrystall about their property in the Flockton Basin. Griffen and Chrystall had to leave their house after the flooding made it unliveable. This video was part of a series of videos about residents in the flood-prone Flockton Basin.

Research papers, University of Canterbury Library

Despite the relatively low seismicity, a large earthquake in the Waikato region is expected to have a high impact, when the fourth-largest regional population and economy and the high density critical infrastructure systems in this region are considered. Furthermore, Waikato has a deep soft sedimentary basin, which increases the regional seismic hazard due to trapping and amplification of seismic waves and generation of localized surface waves within the basin. This phenomenon is known as the “Basin Effect”, and has been attributed to the increased damage in several historic earthquakes, including the 2010-2011 Canterbury earthquakes. In order to quantitatively model the basin response and improve the understanding of regional seismic hazard, geophysical methods will be used to develop shear wave velocity profiles across the Waikato basin. Active surface wave methods involve the deployment of linear arrays of geophones to record the surface waves generated by a sledge hammer. Passive surface wave methods involve the deployment of two-dimensional seismometer arrays to record ambient vibrations. At each site, the planned testing includes one active test and two to four passive arrays. The obtained data are processed to develop dispersion curves, which describe surface wave propagation velocity as a function of frequency (or wavelength). Dispersion curves are then inverted using the Geopsy software package to develop a suite of shear wave velocity profiles. Currently, more than ten sites in Waikato are under consideration for this project. This poster presents the preliminary results from the two sites that have been tested. The shear wave velocity profiles from all sites will be used to produce a 3D velocity model for the Waikato basin, a part of QuakeCoRE flagship programme 1.

Research papers, University of Canterbury Library

Oblique convergence of the Pacific and Australian Plates is accommodated in the northern South Island by the Marlborough Fault System. The Hope Fault is the southern of four major dextral strike-slip faults of this system. Hanmer Basin is a probable segment boundary between the Hope River and Conway segments of the Hope Fault. The Conway segment is transpressional and shows increasing structural complexity near the segment boundary at Hanmer Basin, with multiple Late Quaternary traces, and fault-parallel folding in response to across-fault shortening. Between Hossack Station and Hanmer Basin a crush zone in excess of one kilometre wide is exposed in incised streams and rivers. The crush zone has an asymmetrical geometry about the active trace of the Hope Fault, being only 100-300 metres wide south of the fault, and more than 500 metres wide north of the fault. The most intense deformation of Torlesse bedrock occurs at the south side of the fault zone, indicating that strain is accommodated against the fault footwall. North of the fault deformation is less intense, but occurs over a wider area. The wide fault zone at Hossack Station may reflect divergence of the Hanmer Fault, a major splay of the Hope Fault. At Hossack Station, the Hope Fault has accommodated at least 260 metres of dextral displacement during the Holocene. Dating of abandoned stream channels, offset by the Hope Fault, indicated a Late Holocene dextral slip-rate of 18±8 mm-¹ for the west end of the Conway segment. Using empirical formulae and inferred fault parameters, the expected magnitude of an earthquake generated by the Conway segment is M6.9 to M7.4; for an exceedence probability of 10%, the magnitude is M7.7 to M7.9. Effects associated with coseismic rupture of the Conway segment include shaking of up to MMIX along the ruptured fault and at Hanmer Basin. Uplift at the east end of Hanmer Basin, in conjunction with subsidence at the southwest margin of the basin, is resulting in the development of onlapping stratigraphy. Seismic reflection profiles support this theory. Possible along-fault migration of the basin is inferred to be a consequence of non-parallelism of the master faults.

Research papers, University of Canterbury Library

This paper provides an overview of the salient aspects of the dense array of ground motions observed in the 4 September 2010 Darfield and 22 February 2011 Christchurch earthquakes. Particular attention is given to inferred physical reasons for the observed ground motions, which include: (i) source features such as forward directivity effects; (ii) The effects of the Canterbury Plains sedimentary basin on basin-generated surface waves, and waveguide effects through the region; and (iii) the importance of local site response as evidenced by observations of large long period amplification and liquefaction. The significance of vertical ground motion intensity is also examined.

Research papers, University of Canterbury Library

This article presents a quantitative case study on the site amplification effect observed at Heathcote Valley, New Zealand, during the 2010-2011 Canterbury earthquake sequence for 10 events that produced notable ground acceleration amplitudes up to 1.4g and 2.2g in the horizontal and vertical directions, respectively. We performed finite element analyses of the dynamic response of the valley, accounting for the realistic basin geometry and the soil non-linear response. The site-specific simulations performed significantly better than both empirical ground motion models and physics based regional-scale ground motion simulations (which empirically accounts for the site effects), reducing the spectral acceleration prediction bias by a factor of two in short vibration periods. However, our validation exercise demonstrated that it was necessary to quantify the level of uncertainty in the estimated bedrock motion using multiple recorded events, to understand how much the simplistic model can over- or under-estimate the ground motion intensities. Inferences from the analyses suggest that the Rayleigh waves generated near the basin edge contributed significantly to the observed high frequency (f>3Hz) amplification, in addition to the amplification caused by the strong soil-rock impedance contrast at the site fundamental frequency. Models with and without considering soil non-linear response illustrate, as expected, that the linear elastic assumption severely overestimates ground motions in high frequencies for strong earthquakes, especially when the contribution of basin edge-generated Rayleigh waves becomes significant. Our analyses also demonstrate that the effect of pressure-dependent soil velocities on the high frequency ground motions is as significant as the amplification caused by the basin edge-generated Rayleigh waves.

Research papers, University of Canterbury Library

This presentation summarizes the development of high-resolution surficial soil velocity models in the Canterbury, New Zealand basin. Shallow (<30m) shear wave velocities were primarily computed based on a combination of a large database of over 15,000 cone penetration test (CPT) logs in and around Christchurch, and a recently-developed Christchurch-specific empirical correlation between soil shear wave velocity and CPT. Large active-source testing at 22 locations and ambient-wavefield surface wave and H/V testing at over 80 locations were utilized in combination with 1700 water well logs to constrain the inter-bedded stratigraphy and velocity of Quaternary sediments up to depths of several hundred meters. Finally, seismic reflection profiles and the ambient-wavefield surface wave data provide constraint on velocities from several hundred meters to several kilometres. At all depths, the high resolution data illustrates the complexity of the soil conditions in the region, and the developed 3D models are presently being used in broadband ground motion simulations to further interpret the observed strong ground motions in the 2010-2011 Canterbury earthquake sequence.

Research papers, University of Canterbury Library

The November 2016 MW 7.8 Kaikōura Earthquake initiated beneath the North Culverden basin on The Humps fault and propagated north-eastwards, rupturing at least 17 faults along a cumulative length of ~180 km. The geomorphic expression of The Humps Fault across the Emu Plains, along the NW margin of Culverden basin, comprises a series of near-parallel strands separated by up to 3 km across strike. The various strands strike east to east-northeast and have been projected to mainly dip steeply to the south in seismic data (~80°). In this area, the fault predominantly accommodates right-lateral slip, with uplift and subsidence confined to releasing and restraining bends and step-overs at a range of scales. The Kaikōura event ruptured pre-existing fault scarps along the Emu Plains, which had been partly identified prior to the earthquake. Geomorphology and faulting expression of The Humps Fault on The Emu Plains was mapped, along with faulting related structures which did not rupture in the 2016 earthquake. Fault ruptures strands are combined into sections and the kinematic deformation of sections analysed to provide a moment tensor fault plane solution. This fault plane solution is consistent with the regional principal horizontal shortening direction (PHS) of ~115°, similar to seismic focal mechanism solutions of some of the nearby aftershocks of the Kaikōura earthquake, and similar to the adjacent Hope Fault. To constrain the timing of paleoseismic events, a trench was excavated across the fault where it crossed a late Quaternary alluvial fan. Mapping of stratigraphy exposed in the trench walls, and dating of variably deformed strata, constrains the pre-historic earthquake event history at the trench site. The available data provides evidence for at least three paleo-earthquakes within the last 15.1 ka, with a possible fourth (penultimate) event. These events are estimated to have occurred at 7.7-10.3 ka, 10.3-14.8 ka, and one or more events that are older than ~15.1 ka. Some evidence suggests an additional penultimate event between 1850 C.E and 7.7 ka. Time-integrated slip-rates at three locations on the fault are measured using paleo-channels as piercing points. These sites give horizontal slip rates of 0.57 ± 0.1 mm/year, 0.49 ± 0.1 mm/year and one site constrains a minimum of between 0.1 - 0.4 mm/year. Two vertical slip-rates are calculated to be constrained to a maximum of 0.2 ± 0.02 mm/year at one site and between 0.02 and 0.1 mm/year at another site. Prior to this study, The Humps fault had only been partially documented in reconnaissance level mapping in the district, and no previous paleoseismic or slip rate data had been reported. This project has provided a detailed fault zone tectonic geomorphic map and established new slip-rate and paleoseismic data. The results highlight that The Humps fault plays an important role in regional seismicity and in accommodating plate boundary deformation across the North Canterbury region.

Audio, Radio New Zealand

Australian cricket legend Shane Warne is top billing on an all-star lineup of former cricketers and sporting personalities for a Christchurch earthquake appeal charity match in Wellington on Sunday March the 13th. Warne will play in Stephen Fleming's Canterbury Invitation Eleven against Martin Crowe's Wellington Legends at the Basin Reserve.

Images, Alexander Turnbull Library

PM John Key sits at a large desk in a very large chair looking disconcerted as a messenger says 'after your display in the charity match - John Wright wants you on standby for India. Context - The charity match for Christchurch played at the Basin reserve on Sunday 9 March 2011. The prime minister played along with actors Russell Crowe and James Nesbitt, who were opposing coaches with the match being refereed by Ian McKellen in Sunday's match starting at 4pm. Key will face an over from the Australian spin king during the innings break at the Basin, which Cricket Wellington expects could sell out as early as today. Quantity: 1 digital cartoon(s).

Images, UC QuakeStudies

A photograph of members of a church group holding shovels and spades. The group is volunteering their time in the Flockton Basin, a flood-prone residential area that underwent major flooding in March and April 2014. All Right? posted the photograph on their Facebook page on 7 March 2014 at 11:02am.

Research papers, University of Canterbury Library

This paper provides a summary of the ground motions observed in the recent Canterbury, New Zealand earthquake sequence. The sequence occurred in a region of relatively moderate seismicity, 130km to the east of the Alpine Fault, the major plate-boundary in the region. From an engineering perspective, the sequence has been primarily comprised of the initial 04/09/2010 Darfield earthquake (Mw7.1) followed by the 22/02/2011 Christchurch earthquake (Mw6.3), and two aftershocks on 13/06/ 2011 (Mw5.3 and 6.0, respectively). The dense spacing of strong motions in the region, and their close proximity to the respective causative faults, has resulted in strong ground motions far exceeding the previous catalogue of strong motion observed in New Zealand. The observed ground motions have exhibited clear evidence of: (i) near-source directivity; (ii) sedimentary basin focusing, amplification and basin effect refraction; (iii) non-linear site response; (iv) cyclic mobility postliquefaction; and (v) extreme vertical ground motions exceeding 2g, among others.

Research papers, University of Canterbury Library

This dissertation addresses a diverse range of topics in the physics-based broadband ground motion simulation, with a focus on New Zealand applications. In particular the following topics are addressed: the methodology and computational implementation of a New Zealand Velocity Model for broadband ground motion simulation; generalised parametric functions and spatial correlations for seismic velocities in the Canterbury, New Zealand region from surface-wave-based site characterisation; and ground motion simulations of Hope Fault earthquakes. The paragraphs below outline each contribution in more detail. A necessary component in physics-based ground motion simulation is a 3D model which details the seismic velocities in the region of interest. Here a velocity model construction methodology, its computational implementation, and application in the construction of a New Zealand velocity model for use in physics-based broadband ground motion simulation are presented. The methodology utilises multiple datasets spanning different length scales, which is enabled via the use of modular sub-regions, geologic surfaces, and parametric representations of crustal velocity. A number of efficiency-related workflows to decrease the overall computational construction time are employed, while maintaining the flexibility and extensibility to incorporate additional datasets and re- fined velocity parameterizations as they become available. The model comprises explicit representations of the Canterbury, Wellington, Nelson-Tasman, Kaikoura, Marlborough, Waiau, Hanmer and Cheviot sedimentary basins embedded within a regional travel-time tomography-based velocity model for the shallow crust and provides the means to conduct ground motion simulations throughout New Zealand for the first time. Recently developed deep shear-wave velocity profiles in Canterbury enabled models that better characterise the velocity structure within geologic layers of the Canterbury sedimentary basin to be developed. Here the development of depth- and Vs30-dependent para-metric velocity and spatial correlation models to characterise shear-wave velocities within the geologic layers of the Canterbury sedimentary basin are presented. The models utilise data from 22 shear-wave velocity profiles of up to 2.5km depth (derived from surface wave analysis) juxtaposed with models which detail the three-dimensional structure of the geologic formations in the Canterbury sedimentary basin. Parametric velocity equations are presented for Fine Grained Sediments, Gravels, and Tertiary layer groupings. Spatial correlations were developed and applied to generate three-dimensional stochastic velocity perturbations. Collectively, these models enable seismic velocities to be realistically represented for applications such as 3D ground motion and site response simulations. Lastly the New Zealand velocity model is applied to simulate ground motions for a Mw7.51 rupture of the Hope Fault using a physics-based simulation methodology and a 3D crustal velocity model of New Zealand. The simulation methodology was validated for use in the region through comparison with observations for a suite of historic small magnitude earthquakes located proximal to the Hope Fault. Simulations are compared with conventionally utilised empirical ground motion models, with simulated peak ground velocities being notably higher in regions with modelled sedimentary basins. A sensitivity analysis was undertaken where the source characteristics of magnitude, stress parameter, hypocentre location and kinematic slip distribution were varied and an analysis of their effect on ground motion intensities is presented. It was found that the magnitude and stress parameter strongly influenced long and short period ground motion amplitudes, respectively. Ground motion intensities for the Hope Fault scenario are compared with the 2016 Kaikoura Mw7.8 earthquake, it was found that the Kaikoura earthquake produced stronger motions along the eastern South Island, while the Hope Fault scenario resulted in stronger motions immediately West of the near-fault region. The simulated ground motions for this scenario complement prior empirically-based estimates and are informative for mitigation and emergency planning purposes.

Research papers, University of Canterbury Library

This manuscript provides a critical examination of the ground motions recorded in the near-source region resulting from the 22 February 2011 Christchurch earthquake. Particular attention is given to reconciling the observed spatial distribution of ground motions in terms of physical phenomena related to source, path and site effects. The large number of near-source observed strong ground motions show clear evidence of: forward-directivity, basin generated surface waves, liquefaction and other significant nonlinear site response. The pseudo-acceleration response spectra (SA) amplitudes and significant duration of strong motions agree well with empirical prediction models, except at long vibration periods where the influence of basin-generated surface waves and nonlinear site response are significant and not adequately accounted for in empirical SA models. Pseudo-acceleration response spectra are also compared with those observed in the 4 September 2010 Darfield earthquake and routine design response spectra used in order to emphasise the amplitude of ground shaking and elucidate the importance of local geotechnical characteristics on surface ground motions. The characteristics of the observed vertical component accelerations are shown to be strongly dependent on source-to-site distance and are comparable with those from the 4 September 2010 Darfield earthquake, implying the large amplitudes observed are simply a result of many observations at close distances rather than a peculiar source effect.

Research papers, University of Canterbury Library

© 2017 The Royal Society of New Zealand. This paper discusses simulated ground motion intensity, and its underlying modelling assumptions, for great earthquakes on the Alpine Fault. The simulations utilise the latest understanding of wave propagation physics, kinematic earthquake rupture descriptions and the three-dimensional nature of the Earth's crust in the South Island of New Zealand. The effect of hypocentre location is explicitly examined, which is found to lead to significant differences in ground motion intensities (quantified in the form of peak ground velocity, PGV) over the northern half and southwest of the South Island. Comparison with previously adopted empirical ground motion models also illustrates that the simulations, which explicitly model rupture directivity and basin-generated surface waves, lead to notably larger PGV amplitudes than the empirical predictions in the northern half of the South Island and Canterbury. The simulations performed in this paper have been adopted, as one possible ground motion prediction, in the ‘Project AF8’ Civil Defence Emergency Management exercise scenario. The similarity of the modelled ground motion features with those observed in recent worldwide earthquakes as well as similar simulations in other regions, and the notably higher simulated amplitudes than those from empirical predictions, may warrant a re-examination of regional impact assessments for major Alpine Fault earthquakes.

Audio, Radio New Zealand

Topics - ready with the pumps at last this time, but thankfully not as much rain - so far - as feared for people in the low-lying Flockton Basin in Christchurch. Labour's proposing a special court be set up just to deal with earthquake insurance claims, as part of a policy around the Christchurch rebuild. The policy would see an Earthquake Court established to try to speed up the settling of 9,755 outstanding "over cap" insurance claims. John Banks will be gone by Friday from Parliament, at the behest of the ACT party with a gentle nudge from the Nats as well. The PM thinks it's a joke that the Civilian political party, run by Ben Uffindell and named after his satirical webite, will receive $33,000 of taxpayer funding for the coming election.

Research papers, University of Canterbury Library

his poster presents the ongoing development of a 3D Canterbury seismic velocity model which will be used in physics-based hybrid broadband ground motion simulation of the 2010-2011 Canterbury earthquakes. Velocity models must sufficiently represent critical aspects of the crustal structure over multiple length scales which will influence the results of the simulations. As a result, numerous sources of data are utilized in order to provide adequate resolution where necessary. Figure 2: (a) Seismic reflection line showing P-wave velocities and significant geologic horizons (Barnes et al. 2011), and (b) Shear wave profiles at 10 locations (Stokoe et al. 2013). Figure 4: Cross sections of the current version of the Canterbury velocity model to depths of 10km as shown in Figure 1: (a) at a constant latitude value of -43.6˚, and (b) at a constant longitude value of 172.64˚. 3. Ground Surface and Geologic Horizon Models Figure 3: (a) Ground surface model derived from numerous available digital elevation models, and (b) Base of the Quaternary sediments derived from structural contours and seismic reflection line elevations. The Canterbury region has a unique and complex geology which likely has a significant impact on strong ground motions, in particular the deep and loose deposits of the Canterbury basin. The Canterbury basin has several implications on seismic wave phenomena such as long period ground motion amplification and wave guide effects. Using a realistic 3D seismic velocity model in physics-based ground motion simulation will implicitly account for such effects and the resultant simulated ground motions can be studied to gain a fundamental understanding of the salient ground motion phenomena which occurred during the Canterbury earthquakes, and the potential for repeat occurrences in the Canterbury region. Figure 1 shows the current model domain as a rectangular area between Lat=[-43.2˚,-44.0˚], and Lon=[171.5˚,173.0˚]. This essentially spans the area between the foot of the Southern Alps in the North West to Banks Peninsula in the East. Currently the model extends to a depth of 50km below sea level.

Research papers, University of Canterbury Library

This paper presents the ongoing development of a new 3D seismic velocity model of Canterbury, New Zealand. The model explicitly represents the Canterbury sedimentary basin, and other significant geologic horizons, which are expected to have important implications on observed ground motions. The model utilizes numerous sources of data, including 3D regional tomography with a variable-depth inferred Moho, seismic reflection survey lines, geotechnical boreholes and well logs, spectral analysis of surface waves, and CPT logs which provide velocity constraints over their respective ranges of application. The model provides P- and S-wave velocity and density (i.e. Vp, Vs and p) over a grid of input points, and is presently being utilized in broadband ground motion simulations of the 2010-2011 Canterbury earthquakes. Comparison of simulated ground motions with those observed in the 2010-2011 Canterbury earthquakes will help provide a better understanding of the salient physical processes which characterized the unique set of strong ground motions recorded in this sequence of earthquake events.

Research papers, University of Canterbury Library

In this paper, we perform hybrid broadband (0-10 Hz) ground motion simulations for the ten most significant events (Mw 4.7-7.1) in the 2010-2011 Canterbury earthquake sequence. Taking advantage of having repeated recordings at same stations, we validate our simulations using both recordings and an empirically-developed ground motion prediction equation (GMPE). The simulation clearly captures the sedimentary basin amplification and the rupture directivity effects. Quantitative comparisons of the simulations with both recordings and the GMPE, as well as analyses of the total residuals (indicating model bias) show that simulations perform better than the empirical GMPE, especially for long period. To scrutinize the ground motion variability, we partitioned the total residuals into different components. The total residual appears to be unbiased, and the use of a 3D velocity structure reduces the long period systematic bias particularly for stations located close to the Banks Peninsula volcanic area.