- The Avon-Ōtākaro Redzone is an 11 kilometer stretch of land along the Avon-Ōtākaro River in Christchurch. - This project focused on the creation of a publicly available biodiversity map of the AvonŌtākaro River Corridor, a project undertaken as part of the ecological restoration of the Christchurch redzone. - This project originated from the Christchurch 2010-2011 earthquake sequence which saw liquefaction damage along 11km of the Avon River. Under guidance from The Nature Lab & Ōtākaro Living Laboratory, and various other experts, the primary research objective was to map historical biodiversity, identify hotspots, and assess areas for potential revegetation. - The data collected came from historical black maps, current iNaturalist data, and soil classification information. - The findings show that, pre-colonialism, the area was composed of herbaceous areas, wetlands, native shrubland, and tussock land, with key plants such as river, fern, tutu, and cabbage trees. - The post-earthquake analysis shows a transition from a residential area to patchy grasslands and swampy areas. - The findings also showed a strong relationship between historic sites and soil classifications, providing knowledge for past and future vegetation patterns and spread. - This map will be a valuable resource for conservation efforts and public engagement as the area transitions into a blue-green corridor.
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This paper presents a methodology by which both site-specific and spatially distributed ground motion intensity can be obtained immediately following an earthquake event. The methodology makes use of both prediction models for ground motion intensity and its correlation over spatial distances. A key benefit of the methodology is that the ground motion intensity at a given location is not a single value but a distribution of values. The distribution is comprised of both a mean and also standard deviation, with the standard deviation being a function of the distance to nearby strong motion stations. The methodology is illustrated for two applications. Firstly, maps of conditional peak ground acceleration (PGA) have been developed for the major events in the Canterbury earthquake sequence. It is illustrated how these conditional maps can be used for post-event evaluation of liquefaction triggering criteria which have been adopted by the Department of Building and Housing (DBH). Secondly, the conditional distribution of response spectral ordinates is obtained at a specific location for the purposes of determining appropriate ground motion records for use in seismic response analyses of important structures at locations where direct recordings are absent.
This paper summarizes the development of a high-resolution surficial shear wave velocity model based on the combination of the large high-spatial-density database of cone penetration test (CPT) logs in and around Christchurch, New Zealand and a recently-developed Christchurch-specific empirical correlation between soil shear wave velocity and CPT. This near-surface shear wave velocity model has applications for site characterization efforts via the development of maps of time-averaged shear wave velocities over specific depths, as well as use in site response analysis and ground motion simulation.
This paper summarizes the development of a region-wide surficial shear wave velocity model based on the combination of the large high-spatial-density database of cone penetration test (CPT) logs in and around Christchurch, New Zealand and a recently-developed Christchurch-specific empirical correlation between soil shear wave velocity and CPT. The ongoing development of this near-surface shear wave velocity model has applications for site characterization efforts via the development of maps of time-averaged shear wave velocities over specific depths, and the identification of regional similarities and differences in soil shear stiffness.
A 3D high-resolution model of the geologic structure and associated seismic velocities in the Canterbury, New Zealand region is developed utilising data from depthconverted 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, developed using geostatistical Kriging, explicitly represents the significant and regionally recognisable geologic surfaces that mark the boundaries between geologic units with distinct lithology and age. The model is examined in the form of both geologic surface elevation contour maps as well as vertical cross sections of shear wave velocity, with the most prominent features being the Banks Peninsula Miocene-Pliocene volcanic edifice, and the Pegasus and Rakaia late Mesozoic-Neogene sedimentary basins. The adequacy of the modelled geologic surfaces is assessed through a residual analysis of point constraints used in the Kriging and qualitative comparisons with previous geologic models of subsets of the region. Seismic velocities for the lithological units between the geologic surfaces have also been derived, thus providing the necessary information for a Canterbury velocity model (CantVM) for use in physics-based seismic wave propagation. The developed model also has application for the determination of depths to specified shear wave velocities for use in empirical ground motion modelling, which is explicitly discussed via an example.
Surface rupture and slip from the Mw 7.8 2016 Kaikōura Earthquake have been mapped in the region between the Leader and Charwell rivers using field mapping and LiDAR data. The eastern Humps, north Leader and Conway-Charwell faults ruptured the ground surface in the study area. The E-NE striking ‘The Humps’ Fault runs along the base of the Mt Stewart range front, appears to dip steeply NW and intersects the NNW-NNE Leader Fault which itself terminates northwards at the NE striking Conway-Charwell Fault. The eastern Humps Fault is up to the NW and accommodates oblique slip with reverse and right lateral displacement. Net slip on ‘The Humps’ Fault is ≤4 m and produced ≤4 m uplift of the Mt Stewart range during the earthquake. The Leader Fault strikes NNW-NNE with dips ranging from ~10° west to 80° east and accommodated ≤4 m net slip comprising left-lateral and up-to-the-west vertical displacement. Like the Humps west of the study area, surface-rupture of the Leader Fault occurred on multiple strands. The complexity of rupture on the Leader Fault is in part due to the occurrence of bedding-parallel slip within the Cretaceous-Cenozoic sequence. Although the Mt Stewart range front is bounded by ‘The Humps’ Fault, in the study area neither this fault nor the Leader Fault were known to have been active before the earthquake. Fieldwork and trenching investigations are ongoing to characterise the geometry, kinematics and paleoseismic history of the mapped active faults.
On 14 November 2016, the Mw 7.8 Kaikōura earthquake caused widespread damage along the east coast of the South Island, New Zealand. Kaikōura town itself was isolated from the rest of the country by landslides blocking off major roads. While impacts from the Kaikōura earthquake on large, urban population centres have been generally well documented, this thesis aims to fill gaps in academic knowledge regarding small rural towns. This thesis investigates what, where and when critical infrastructure and lifeline service disruption occurred following the 2016 Kaikōura earthquake in a selection of small towns, and how the communities in these areas adapted to disruption. Following a robust review of literature and news media, four small rural towns were selected from North Canterbury (Culverden & Waiau) and Marlborough (Seddon & Ward) in the South Island, New Zealand. Semi-structured interview sessions with a special focus on these towns were held with infrastructure managers, emergency response and recovery officials, and organisation leaders with experience or expertise in the 2016 Kaikōura earthquake. Findings were supplemented with emergency management situation reports to produce hazard maps and infrastructure exposure maps. A more detailed analysis was conducted for Waiau involving interdependence analyses and a level of service timeline for select lifeline services. The earthquake impacted roads by blocking them with landslides, debris and surface rupture. Bridges where shaken off their abutments, breaking infrastructure links such as fibre landlines as they went. Water supplies and other forms of infrastructure relied heavily on the level of service of roads, as rough rural terrain left few alternatives. Adapting to an artificial loss of road service, some Waiau locals created their own detour around a road cordon in order to get home to family and farms. Performance of dwellings was tied to socioeconomic factors as much as proximity to the epicentre. Farmers who lost water access pulled out fences to allow stock to drink from rivers. Socioeconomic differences between farmland and township residents also contributed to resilience variations between the towns assessed in this study. Understanding how small rural towns respond and adapt to disaster allows emergency management officials and policy to be well informed and flexible with planning for multiple size classes of towns.
The Canterbury Earthquake Sequence (CES) of 2010-2011 produced large seismic moments up to Mw 7.1. These large, near-to-surface (<15 km) ruptures triggered >6,000 rockfall boulders on the Port Hills of Christchurch, many of which impacted houses and affected the livelihoods of people within the impacted area. From these disastrous and unpredicted natural events a need arose to be able to assess the areas affected by rockfall events in the future, where it is known that a rockfall is possible from a specific source outcrop but the potential boulder runout and dynamics are not understood. The distribution of rockfall deposits is largely constrained by the physical properties and processes of the boulder and its motion such as block density, shape and size, block velocity, bounce height, impact and rebound angle, as well as the properties of the substrate. Numerical rockfall models go some way to accounting for all the complex factors in an algorithm, commonly parameterised in a user interface where site-specific effects can be calibrated. Calibration of these algorithms requires thorough field checks and often experimental practises. The purpose of this project, which began immediately following the most destructive rupture of the CES (February 22, 2011), is to collate data to characterise boulder falls, and to use this information, supplemented by a set of anthropogenic boulder fall data, to perform an in-depth calibration of the three-dimensional numerical rockfall model RAMMS::Rockfall. The thesis covers the following topics: • Use of field data to calibrate RAMMS. Boulder impact trails in the loess-colluvium soils at Rapaki Bay have been used to estimate ranges of boulder velocities and bounce heights. RAMMS results replicate field data closely; it is concluded that the model is appropriate for analysing the earthquake-triggered boulder trails at Rapaki Bay, and that it can be usefully applied to rockfall trajectory and hazard assessment at this and similar sites elsewhere. • Detailed analysis of dynamic rockfall processes, interpreted from recorded boulder rolling experiments, and compared to RAMMS simulated results at the same site. Recorded rotational and translational velocities of a particular boulder show that the boulder behaves logically and dynamically on impact with different substrate types. Simulations show that seasonal changes in soil moisture alter rockfall dynamics and runout predictions within RAMMS, and adjustments are made to the calibration to reflect this; suggesting that in hazard analysis a rockfall model should be calibrated to dry rather than wet soil conditions to anticipate the most serious outcome. • Verifying the model calibration for a separate site on the Port Hills. The results of the RAMMS simulations show the effectiveness of calibration against a real data set, as well as the effectiveness of vegetation as a rockfall barrier/retardant. The results of simulations are compared using hazard maps, where the maximum runouts match well the mapped CES fallen boulder maximum runouts. The results of the simulations in terms of frequency distribution of deposit locations on the slope are also compared with those of the CES data, using the shadow angle tool to apportion slope zones. These results also replicate real field data well. Results show that a maximum runout envelope can be mapped, as well as frequency distribution of deposited boulders for hazard (and thus risk) analysis purposes. The accuracy of the rockfall runout envelope and frequency distribution can be improved by comprehensive vegetation and substrate mapping. The topics above define the scope of the project, limiting the focus to rockfall processes on the Port Hills, and implications for model calibration for the wider scientific community. The results provide a useful rockfall analysis methodology with a defensible and replicable calibration process, that has the potential to be applied to other lithologies and substrates. Its applications include a method of analysis for the selection and positioning of rockfall countermeasure design; site safety assessment for scaling and demolition works; and risk analysis and land planning for future construction in Christchurch.
In this paper we introduce CityViewAR, a mobile outdoor Augmented Reality (AR) application for providing AR information visualization on a city scale. The CityViewAR application was developed to provide geographical information about the city of Christchurch, which was hit by several major earthquakes in 2010 and 2011. The application provides information about destroyed buildings and historical sites that were affected by the earthquakes. The geo-located content is provided in a number of formats including 2D map views, AR visualization of 3D models of buildings on-site, immersive panorama photographs, and list views. The paper describes the iterative design and implementation details of the application, and gives one of the first examples of a study comparing user response to AR and non-AR viewing in a mobile tourism application. Results show that making such information easily accessible to the public in a number of formats could help people to have richer experience about cities. We provide guidelines that will be useful for people developing mobile AR applications for city-scale tourism or outdoor guiding, and discuss how the underlying technology could be used for applications in other areas.
This paper presents site-specific and spatially-distributed ground-motion intensity estimates which have been utilized in the aftermath of the 2010-2011 Canterbury, New Zealand earthquakes. The methodology underpinning the ground motion intensity estimation makes use of both prediction models for ground motion intensity and its within-event spatial correlation. A key benefit of the methodology is that the estimated ground motion intensity at a given location is not a single value but a distribution of values. The distribution is comprised of both a mean and standard deviation, with the standard deviation being a function of the distance to nearby observations at strong motion stations. The methodology is illustrated for two applications. Firstly, maps of conditional peak ground acceleration (PGA) have been developed for the major events in the Canterbury earthquake sequence, which among other things, have been utilized for assessing liquefaction triggering susceptibility of land in residential areas. Secondly, the conditional distribution of response spectral ordinates is obtained at the location of the Canterbury Television building (CTV), which catastrophically collapsed in the 22 February 2011 earthquake. The conditional response spectra provide insight for the selection of ground motion records for use in forensic seismic response analyses of important structures at locations where direct recordings are absent.
This poster provides a summary of the development of a 3D shallow (z<40m) shear wave velocity (Vs) model for the urban Christchurch, New Zealand region. The model is based on a recently developed Christchurch-specific empirical correlation between Vs and cone penetration test (CPT) data (McGann et al. 2014a,b) and the large high-density database of CPT logs in the greater Christchurch urban area (> 15,000 logs as of 01/01/2014). In particular, the 3D model provides shear wave velocities for the surficial Springston Formation, Christchurch Formation, and Riccarton gravel layers which generally comprise the upper 40m in the Christchurch urban area. Point-estimates are provided on a 200m-by- 200m grid from which interpolation to other locations can be performed. This model has applications for future site characterization and numerical modeling efforts via maps of timeaveraged Vs over specific depths (e.g. Vs30, Vs10) and via the identification of typical Vs profiles for different regions and soil behaviour types within Christchurch. In addition, the Vs model can be used to constrain the near-surface velocities for the 3D seismic velocity model of the Canterbury basin (Lee et al. 2014) currently being developed for the purpose of broadband ground motion simulation.
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.
Sea level rise is one consequence of Earth’s changing climate. Century-long tide gauge records show that global-mean sea-level rise reached 11-16 cm during the twentieth century at a mean rate of 1.2 mm/y. Today, the average rate of global-mean sea-level rise is higher at 3-4 mm/y and is expected to increase in the future. This represents a hazard to low elevation coastal zones worldwide. Yet, before global sea level projections can be used to characterise future coastal flood hazard at a local scale, the effects of tectonics (and other processes) that drive vertical land motion (VLM) must be considered. VLM is defined as the vertical velocity (uplift or subsidence) of the solid surface with respect to the centre of Earth. In this study, new VLM maps are generated over coastal strips in New Zealand, using Sentinel-1 InSAR and GNSS data. In New Zealand, measuring VLM using InSAR on naturally vegetated or agricultural land is difficult due to signal decorrelation. Along the rural Bay of Plenty coastal strip, I use a persistent-scatterer approach to generate a VLM map from both east-looking ascending and west-looking descending Sentinel-1 data between 2015-2021. Using time-series data over the same time period from a dense network of 20 GNSS sensors, I tie InSAR-derived line-of-sight velocity to the 2014 ITRF reference frame. I test two different methods for measuring VLM and compare the results against GNSS vertical velocity along the Bay of Plenty coast. Best results are achieved by first removing the interpolated horizontal GNSS velocity field from each of the InSAR datasets, before averaging the two VLM estimates. Measured VLM is between -3 and 3 mm/y, with negative values (subsidence) occurring within the low-lying Rangitāiki Plain and Ōpōtiki valley, and uplift across the elevated region west of Matatā. This thesis integrates geomorphological, geological, and historical levelling VLM records with modern satellite datasets to assess VLM across timescales ranging from 10 to 100,000 years at Matatā. Uplift rate has been variable through time, with average uplift over the last 300,000 years of 1 mm/y, 4.5 mm/y since 1720 years, 2 mm/y between 1950-1978, and 10 mm/y between 2004-2011. Previous modelling has shown that the best fit to the 2004-2011 rapid uplift rates is an inflating magmatic source at ~10 km depth beneath Matatā. To reconcile all data, I present a VLM model that consists of short-lived periods (7 years) of rapid uplift (10 mm/y), separated by longer periods (30 years) of lower background uplift (3 mm/y). The episodic nature of VLM at Matatā likely reflects short-lived periods of magmatic intrusion. Episodic VLM characterised by large rates of uplift (10 mm/y) has been seen at Taupō volcano, and other volcanic centers globally. It has been 12 years since the end of the last intrusion episode; this modelling suggest one may expect to observe increased uplift rates at Matatā in the coming decades. Densely populated urban coastal strips are most at risk from the effects of relative sea-level rise. At the same time, anthropogenic activities associated with urbanization, such as groundwater withdrawal, and land reclamation can lead to local land subsidence (LLS), further exacerbating the risk to urban infrastructure. LLS refers to subsidence relative to nearby land area assumed to be stable. In this thesis, I create the first high-resolution (10 m) maps of LLS at six urban coastal strips in New Zealand, with a combined length of 285 km, using Sentinel-1 InSAR data between 2018-2021. This analysis reveals 89% of urban coastal strips are subsiding at rates of -0.5 mm/y or greater, and 11% is subsiding at higher rates of -3.0 mm/y or greater. On average, subsidence is -0.6 to -2.9 mm/y higher at the coastal strip, compared to inland areas occupied by GNSS stations. This analysis also documents highly-localised hotspots of LLS, with subsidence rates of up to -15 mm/y. In Christchurch, rapid and localised subsidence (-8 mm/y) is observed within coastal suburbs New Brighton and Southshore. In most cities, the highest subsidence rates occur on land reclaimed in the early-late twentieth century, and in areas built on Holocene sediment. Time-series analysis of LLS at sites of reclaimed land shows both linear and non-linear rates of deformation over time periods of up to 6-8 years. This thesis highlights the variable exposure to relative sea-level rise of New Zealand coastal strips, and demonstrates that in many cases current rates of VLM should be expected to continue for the next few decades.
The south Leader Fault (SLF) is a newly documented active structure that ruptured the surface during the Mw 7.8 Kaikoura earthquake. The Leader Fault is a NNE trending oblique left lateral thrust that links the predominantly right lateral ‘The Humps’ and Conway-Charwell faults. The present research uses LiDAR at 0.5 m resolution and field mapping to determine the factors controlling the surface geometries and kinematics of the south Leader Fault ruptures at the ground surface. The SLF zone is up to 2km wide and comprises a series of echelon NE-striking thrusts linked by near-vertical N-S striking faults. The thrusts are upthrown to the west by up to 1 m and dip 35-45°. Thrust slip surfaces are parallel with Cretaceous-Cenozoic bedding and may reflect flexural slip folding. By contrast, the northerly striking faults dip steeply (65° west- 85° east), and accommodate up to 3m of oblique left lateral displacement at the ground surface and displace Cenozoic bedding. Some of the SLF has been mapped in bedrock, although none were known to be active prior to the earthquake or have a strong topographic expression. The complexity of fault rupture and the width of the fault zone appears to reflect the occurrence of faulting and folding at the ground surface during the earthquake.
Study region: Christchurch, New Zealand. Study focus: Low-lying coastal cities worldwide are vulnerable to shallow groundwater salinization caused by saltwater intrusion and anthropogenic activities. Shallow groundwater salinization can have cascading negative impacts on municipal assets, but this is rarely considered compared to impacts of salinization on water supply. Here, shallow groundwater salinity was sampled at high spatial resolution (1.3 piezometer/km2 ), then mapped and spatially interpolated. This was possible due to a uniquely extensive set of shallow piezometers installed in response to the 2010–11 Canterbury Earthquake Sequence to assess liquefaction risk. The municipal assets located within the brackish groundwater areas were highlighted. New hydrological insights for the region: Brackish groundwater areas were centred on a spit of coastal sand dunes and inside the meander of a tidal river with poorly drained soils. The municipal assets located within these areas include: (i) wastewater and stormwater pipes constructed from steel-reinforced concrete, which, if damaged, are vulnerable to premature failure when exposed to chloride underwater, and (ii) 41 parks and reserves totalling 236 ha, within which salt-intolerant groundwater-dependent species are at risk. This research highlights the importance of determining areas of saline shallow groundwater in low-lying coastal urban settings and the co-located municipal assets to allow the prioritisation of sites for future monitoring and management.
Small, tight-knit communities, are complex to manage from outside during a disaster. The township of Lyttelton, New Zealand, and the communities of Corsair Bay, Cass Bay, and Rapaki to the east, are especially more so difficult due to the terrain that encloses them, which caused them to be cut-off from Christchurch, the largest city in the South Island, barely 10 km away, after the Mw 7.1 Darfield Earthquake and subsequent Canterbury Earthquake Sequence. Lyttelton has a very strong and deep-rooted community spirit that draws people to want to be a part of Lyttelton life. It is predominantly residential on the slopes, with retail space, service and light industry nestled near the harbour. It has heritage buildings stretching back to the very foundation of Canterbury yet hosts the largest, modern deep-water port for the region. This study contains two surveys: one circulated shortly before the Darfield Earthquake and one circulated in July 2011, after the Christchurch and Sumner Earthquakes. An analytical comparison of the participants’ household preparedness for disaster before the Darfield Earthquake and after the Christchurch and Sumner Earthquakes was performed. A population spatiotemporal distribution map was produced that shows the population in three-hourly increments over a week to inform exposure to vulnerability to natural hazards. The study went on to analyse the responses of the participants in the immediate period following the Chrsitchurch and Sumner Earthquakes, including their homeward and subsequent journeys, and the decision to evacuate or stay in their homes. Possible predictors to a decision to evacuate some or all members of the household were tested. The study also asked participants’ views on the events since September 2010 for analysis.
The 2015 New Zealand strong-motion database provides a wealth of new strong motion data for engineering applications. An important component of this database is the compilation of new site metadata, describing the soil conditions and site response at GeoNet strong motion stations. We have assessed and compiled four key site parameters for the ~460 GeoNet stations that recorded significant historical ground motions. Parameters include: site classification (NZS1170.5), Vs30, fundamental site period (Tsite) and depth to bedrock (Z1.0, i.e. depth to material with Vs > 1000 m/s). In addition, we have assigned a quality estimate (Quality 1 – 3) to these parameters to provide a qualitative estimate of the uncertainty. New highquality Tsite estimates have largely been obtained from newly available HVSR amplification curves and spectral ratios from inversion of regional strong motion data that has been reconciled with available geological information. Good quality Vs30 estimates, typically in urban centres, have also been incorporated following recent studies. Where site-specific measurements of Vs30 are not available, Vs30 is estimated based on surface geology following national Vs30 maps. New Z1.0 values have been provided from 3D subsurface models for Canterbury and Wellington. This database will be used in efforts to guide development and testing of new and existing ground motion prediction models in New Zealand. In particular, it will allow reexamination of the most important site parameters that control and predict site response in a New Zealand setting. Furthermore, it can be used to provide information about suitable rock reference sites for seismological research, and as a guide to site-specific references in the literature. We discuss compilation of the database, preliminary insights so far, and future directions.
High-quality ground motion records are required for engineering applications including response history analysis, seismic hazard development, and validation of physics-based ground motion simulations. However, the determination of whether a ground motion record is high-quality is poorly handled by automation with mathematical functions and can become prohibitive if done manually. Machine learning applications are well-suited to this problem, and a previous feed-forward neural network was developed (Bellagamba et al. 2019) to determine high-quality records from small crustal events in the Canterbury and Wellington regions for simulation validation. This prior work was however limited by the omission of moderate-to-large magnitude events and those from other tectonic environments, as well as a lack of explicit determination of the minimum usable frequency of the ground motion. To address these shortcomings, an updated neural network was developed to predict the quality of ground motion records for all magnitudes and all tectonic sources—active shallow crustal, subduction intraslab, and subduction interface—in New Zealand. The predictive performance of the previous feed-forward neural network was matched by the neural network in the domain of small crustal records, and this level of predictive performance is now extended to all source magnitudes and types in New Zealand making the neural network applicable to global ground motion databases. Furthermore, the neural network provides quality and minimum usable frequency predictions for each of the three orthogonal components of a record which may then be mapped into a binary quality decision or otherwise applied as desired. This framework provides flexibility for the end user to predict high-quality records with various acceptability thresholds allowing for this neural network to be used in a range of applications.
Surface-rupturing earthquakes can trigger the sudden avulsion of river channels, causing rapid and persistent coseismic flooding of previously unaffected areas. This phenomenon, known as fault-rupture-induced river avulsion (FIRA), occurs when fault displacement significantly alters river channel topography. The importance of understanding FIRA as a secondary seismic hazard was highlighted by events during the 2010 Darfield and 2016 Kaikoura earthquakes in New Zealand. This thesis develops a national model to identify and quantify FIRA susceptibility across New Zealand by integrating hydrological datasets (NIWA RiverMaps and Flood Statistics) with active fault information (NZ Active Faults Database and RSQSim earthquake simulations). The methodology applies the F-index framework proposed by McEwan et al. (2023), which quantifies FIRA potential based on the ratio of fault throw plus discharge-dependent depth to bank full depth at each fault-river intersection. The model successfully identified 3,796 potential FIRA-susceptible fault-river intersections nationwide, with 451 involving waterways equal to or larger than the Hororata River. Regional analysis revealed higher concentrations of FIRA-susceptible sites in the Bay of Plenty, Canterbury, and Marlborough regions. Validation against historical events showed the model effectively located known FIRA occurrences from the Kaikoura and Darfield earthquakes, though with some limitations in accurately predicting F-index values due to complex fault displacement patterns and challenges in modelling bank full depths of large, braided rivers. This research establishes New Zealand's first nationwide assessment of fault-induced river avulsion susceptibility. The approach creates a structured methodology for identifying high-risk fault-river intersections and determining which sites require thorough localised examination. The methodology developed offers a template for similar assessments in other tectonically active regions and contributes to improving earthquake hazard assessment and disaster preparedness planning.
The Global Earthquake Model’s (GEM) Earthquake Consequences Database (GEMECD) aims to develop, for the first time, a standardised framework for collecting and collating geocoded consequence data induced by primary and secondary seismic hazards to different types of buildings, critical facilities, infrastructure and population, and relate this data to estimated ground motion intensity via the USGS ShakeMap Atlas. New Zealand is a partner of the GEMECD consortium and to-date has contributed with 7 events to the database, of which 4 are localised in the South Pacific area (Newcastle 1989; Luzon 1990; South of Java 2006 and Samoa Islands 2009) and 3 are NZ-specific events (Edgecumbe 1987; Darfield 2010 and Christchurch 2011). This contribution to GEMECD represented a unique opportunity for collating, comparing and reviewing existing damage datasets and harmonising them into a common, openly accessible and standardised database, from where the seismic performance of New Zealand buildings can be comparatively assessed. This paper firstly provides an overview of the GEMECD database structure, including taxonomies and guidelines to collect and report on earthquake-induced consequence data. Secondly, the paper presents a summary of the studies implemented for the 7 events, with particular focus on the Darfield (2010) and Christchurch (2011) earthquakes. Finally, examples of specific outcomes and potentials for NZ from using and processing GEMECD are presented, including: 1) the rationale for adopting the GEM taxonomy in NZ and any need for introducing NZ-specific attributes; 2) a complete overview of the building typological distribution in the Christchurch CBD prior to the Canterbury earthquakes and 3) some initial correlations between the level and extent of earthquake-induced physical damage to buildings, building safety/accessibility issues and the induced human casualties.
Landslides are significant hazards, especially in seismically-active mountainous regions, where shaking amplified by steep topography can result in widespread landsliding. These landslides present not only an acute hazard, but a chronic hazard that can last years-to-decades after the initial earthquake, causing recurring impacts. The Mw 7.8 Kaikōura earthquake caused more than 20,000 landslides throughout North Canterbury and resulted in significant damage to nationally significant infrastructure in the coastal transport corridor (CTC), isolating Kaikōura from the rest of New Zealand. In the years following, ongoing landsliding triggered by intense rainfall exacerbated the impacts and slowed the recovery process. However, while there is significant research on co-seismic landslides and their initial impacts in New Zealand, little research has explored the evolution of co-seismic landslides and how this hazard changes over time. This research maps landslides annually between 2013 and 2021 to evaluate the changes in pre-earthquake, co-seismic and post-earthquake rates of landsliding to determine how landslide hazard has changed over this time. In particular, the research explores how the number, area, and spatial distribution of landslides has changed since the earthquake, and whether post-earthquake mitigation works have in any way affected the long-term landslide hazard. Mapping of landslides was undertaken using open-source, medium resolution Landsat-8 and Sentinel-2 satellite imagery, with landslides identified visually and mapped as single polygons that capture both the source zone and deposit. Three study areas with differing levels of post-earthquake mitigation are compared: (i) the northern CTC, where the majority of mitigation was in the form of active debris removal; (ii) the southern CTC, where mitigation was primarily via passive protection measures; and (iii) Mount Fyffe, which has had no mitigation works since the earthquake. The results show that despite similar initial impacts during the earthquake, the rate of recovery in terms of landslide rates varies substantially across the three study areas. In Mount Fyffe, the number and area of landslides could take 45 and 22 years from 2021 respectively to return to pre-earthquake levels at the current rate. Comparatively, in the CTC, it could take just 5 years and 3-4 years from 2021 respectively. Notably, the fastest recovery in terms of landslide rates in the CTC was primarily located directly along the transport network, whereas what little recovery did occur in Mount Fyffe appeared to follow no particular pattern. Importantly, recovery rates in the northern CTC were notably higher than in the southern CTC, despite greater co-seismic impacts in the former. Combined, these results suggest the active, debris removal mitigation undertaken in the northern CTC may have had the effect of dramatically reducing the time for landslide rates to return to pre-earthquake levels. The role of slope angle and slope aspect were explored to evaluate if these observations could be driven by local differences in topography. The Mount Fyffe study area has higher slope angles than the CTC as a whole and landslides predominantly occurred on slightly steeper slopes than in the CTC. This may have contributed to the longer recovery times for landsliding in Mount Fyffe due to greater gravitational instability, however the observed variations are minor compared to the differences in recovery rates. In terms of slope aspect, landslides in Mount Fyffe preferentially occurred on north- and south-facing slopes whereas landslides in the CTC preferred the east- and south-facing slopes. The potential role of these differences in landslide recovery remains unclear but may be related to the propagation direction of the earthquake and the tracking direction of post-earthquake ex-tropical cyclones. Finally, landslides in the CTC are observed to be moving further away from the transport network and the number of landslides impacting the CTC decreased significantly since the earthquake. Nevertheless, the potential for further landslide reactivation remains. Therefore, despite the recovery in the CTC, it is clear that there is still risk of the transport network being impacted by further landsliding, at least for the next 3-5 yrs.
The Covid-19 pandemic has brought to the foreground the importance of social connectedness for wellbeing, at the individual, community and societal level. Within the context of the local community, pro-connection facilities are fundamental to foster community development, resilience and public health. Through identifying the gap in social connectedness literature for Māori, this has created space for new opportunities and to reflect on what is already occurring in Ōtautahi. It is well documented that Māori experience unequal societal impacts across all health outcomes. Therefore, narrowing the inequities between Māori and non-Māori across a spectrum of dimensions is a priority. Evaluating the #WellconnectedNZ project, which explores the intersections between social connection and wellbeing is one way to trigger these conversations. This was achieved by curating a dissimilar set of community pro-connection facilities and organizing them into a Geographic Information System (GIS). Which firstly involved, the collecting and processing of raw data, followed by spatial analysis through creating maps, this highlighted the alignment between the distribution of places, population and social data. Secondly, statistical analysis focusing on the relationship between deprivation and accessibility. Finally, semi-structured interviews providing perceptions of community experience. This study describes findings following a kaupapa Māori research approach. Results demonstrated that, in general some meshblocks in Ōtautahi benefit from a high level of accessibility to pro-connection facilities; but with an urban-rural gradient (as is expected, further from the central business district (CBD) are less facilities). Additionally, more-deprived meshblocks in the Southern and Eastern suburbs of Christchurch have poorer accessibility, suggesting underlying social and spatial inequalities, likely exacerbated by Covid-19 and the Christchurch earthquakes. In this context, it is timely to (re)consider pro-connection places and their role in the development of social infrastructure for connected communities, in the community facility planning space. ‘We are all interwoven, we just need to make better connections’.
A zone of active tectonism occurs in mid and north Canterbury, from the Rakaia to the Waipara Rivers, which coincides with seismicity concentrations and several Quaternary surface anomalies and is here defined as the Porters Pass Tectonic Zone. Although parallel to the Marlborough faults to the north, the lack of regional definition suggests this zone is much younger in its inception reflecting a southward movement of the plate rotation vector. The objectives of this study were to map the structures associated with this zone in the segment between the Rakaia and Waimakariri Rivers with detailed analysis concentrated in the upper Kawai Valley. Quaternary offsets on the main lineament of the Porters Pass Fault were traced through the area and evidence for the rate of movement, probable magnitudes and return periods of related seismic events was sought. The basement was found to be complicated by pre-existing deformation structures in Torlesse Group rocks which have been subsequently been re-activated or rotated by recent fault movement probably beginning in the Pleistocene. This phase is dominantly thrusting and uplift has lead to the erosion of most of the overlying sedimentary cover. Remnants of the Cret-Tertiary sediments still remain as fault-bounded packets. Evidence suggests that a change to development of a regional lateral shear associated with the Porters Pass Tectonic Zone transects the thrust system with complex interaction between the older reverse and new strike-slip faults. Offset rates along the segments of the Porters Pass Fault are not well constrained but are believed to be approximately in the range of 11-13 mm/year for at least the last 130,000 years. This rate is similar to other large faults in the Marlborough region. Two earthquake events have been identified and dated at 600 and 2000 years ago, with a magnitude of greater than 6.5. Evidence suggests characteristic earthquakes along the Porters Pass Fault are greater than Magnitude 7. This result has some major ramifications for the expected seismic hazards for nearby Christchurch.
The Canterbury earthquake sequence (2010-2011) was the most devastating catastrophe in New Zealand‘s modern history. Fortunately, in 2011 New Zealand had a high insurance penetration ratio, with more than 95% of residences being insured for these earthquakes. This dissertation sheds light on the functions of disaster insurance schemes and their role in economic recovery post-earthquakes. The first chapter describes the demand and supply for earthquake insurance and provides insights about different public-private partnership earthquake insurance schemes around the world. In the second chapter, we concentrate on three public earthquake insurance schemes in California, Japan, and New Zealand. The chapter examines what would have been the outcome had the system of insurance in Christchurch been different in the aftermath of the Canterbury earthquake sequence (CES). We focus on the California Earthquake Authority insurance program, and the Japanese Earthquake Reinsurance scheme. Overall, the aggregate cost of the earthquake to the New Zealand public insurer (the Earthquake Commission) was USD 6.2 billion. If a similar-sized disaster event had occurred in Japan and California, homeowners would have received only around USD 1.6 billion and USD 0.7 billion from the Japanese and Californian schemes, respectively. We further describe the spatial and distributive aspects of these scenarios and discuss some of the policy questions that emerge from this comparison. The third chapter measures the longer-term effect of the CES on the local economy, using night-time light intensity measured from space, and focus on the role of insurance payments for damaged residential property during the local recovery process. Uniquely for this event, more than 95% of residential housing units were covered by insurance and almost all incurred some damage. However, insurance payments were staggered over 5 years, enabling us to identify their local impact. We find that night-time luminosity can capture the process of recovery; and that insurance payments contributed significantly to the process of local economic recovery after the earthquake. Yet, delayed payments were less affective in assisting recovery and cash settlement of claims were more effective than insurance-managed repairs. After the Christchurch earthquakes, the government declared about 8000 houses as Red Zoned, prohibiting further developments in these properties, and offering the owners to buy them out. The government provided two options for owners: the first was full payment for both land and dwelling at the 2007 property evaluation, the second was payment for land, and the rest to be paid by the owner‘s insurance. Most people chose the second option. Using data from LINZ combined with data from Stats NZ, the fourth chapter empirically investigates what led people to choose this second option, and how peer effect influenced the homeowners‘ choices. Due to climate change, public disclosure of coastal hazard information through maps and property reports have been used more frequently by local government. This is expected to raise awareness about disaster risks in local community and help potential property owners to make informed locational decision. However, media outlets and business sector argue that public hazard disclosure will cause a negative effect on property value. Despite this opposition, some district councils in New Zealand have attempted to implement improved disclosure. Kapiti Coast district in the Wellington region serves as a case study for this research. In the fifth chapter, we utilize the residential property sale data and coastal hazard maps from the local district council. This study employs a difference-in-difference hedonic property price approach to examine the effect of hazard disclosure on coastal property values. We also apply spatial hedonic regression methods, controlling for coastal amenities, as our robustness check. Our findings suggest that hazard designation has a statistically and economically insignificant impact on property values. Overall, the risk perception about coastal hazards should be more emphasized in communities.
This report summarizes the development of a region-wide surficial soil shear wave velocity (Vs ) model based on the unique combination of a large high-spatial-density database of cone penetration test (CPT) logs in the greater Christchurch urban area (> 15, 000 logs as of 1 February 2014) and the Christchurch-specific empirical correlation between soil Vs and CPT data developed by McGann et al. [1, 2]. This model has applications for site characterization efforts via maps of time-averaged Vs over specific depths (e.g. Vs30, Vs10), and for numerical modeling efforts via the identification of typical Vs profiles for different regions and soil behaviour types within Christchurch. In addition, the Vs model can be used to constrain the near-surface velocities for the 3D seismic velocity model of the Canterbury basin [3] currently being developed for the purpose of broadband ground motion simulation. The general development of these region-wide near-surface Vs models includes the following general phases, with each discussed in separate chapters of this report. • An evaluation of the available CPT dataset for suitability, and the definition of other datasets and assumptions necessary to characterize the surficial sediments of the region to 30 m depth. • The development of time-averaged shear wave velocity (Vsz) surfaces for the Christchurch area from the adopted CPT dataset (and supplementary data/assumptions) using spatial interpolation. The Vsz surfaces are used to explore the characteristics of the near-surface soils in the regions and are shown to correspond well with known features of the local geology, the historical ecosystems of the area, and observations made following the 2010- 2011 Canterbury earthquakes. • A detailed analysis of the Vs profiles in eight subregions of Christchurch is performed to assess the variablity in the soil profiles for regions with similar Vsz values and to assess Vsz as a predictive metric for local site response. It is shown that the distrubution of soil shear wave velocity in the Christchurch regions is highly variable both spatially (horizontally) and with depth (vertically) due to the varied geological histories for different parts of the area, and the highly stratified nature of the nearsurface deposits. This variability is not considered to be greatly significant in terms of current simplified site classification systems; based on computed Vs30 values, all considered regions can be categorized as NEHRP sites class D (180 < Vs < 360 m/s) or E (Vs < 180 m/s), however, detailed analysis of the shear wave velocity profiles in different subregions of Christchurch show that the expected surficial site response can vary quite a bit across the region despite the relative similarity in Vs30
A number of reverse and strike-slip faults are distributed throughout mid-Canterbury, South Island, New Zealand, due to oblique continental collision. There is limited knowledge on fault interaction in the region, despite historical multi-fault earthquakes involving both reverse and strike-slip faults. The surface expression and paleoseismicity of these faults can provide insights into fault interaction and seismic hazards in the region. In this thesis, I studied the Lake Heron and Torlesse faults to better understand the key differences between these two adjacent faults located within different ‘tectonic domains’. Recent activity and surface expression of the Lake Heron fault was mapped and analysed using drone survey, Structure-from-Motion (SfM) derived Digital Surface Model (DSM), aerial image, 5 m-Digital Elevation Model (DEM), luminescence dating technique, and fold modelling. The results show a direct relationship between deformation zone width and the thickness of the gravel deposits in the area. Fold modelling using fault dip, net slip and gravel thickness produces a deformation zone comparable to the field, indicating that the fault geometry is sound and corroborating the results. This result Is consistent with global studies that demonstrate deposit (or soil thickness) correlates to fault deformation zone width, and therefore is important to consider for fault displacement hazard. A geomorphological study on the Torlesse fault was conducted using SfM-DSM, DEM and aerial images Ground Penetrating Radar (GPR) survey, trenching, and radiocarbon and luminescence dating. The results indicate that the Torlesse fault is primarily strike-slip with some dip slip component. In many places, the bedding-parallel Torlesse fault offsets post-glacial deposits, with some evidence of flexural slip faulting due to folding. Absolute dating of offset terraces using radiocarbon dating and slip on fault determined from lateral displacement calculating tool demonstrates the fault has a slip rate of around 0.5 mm/year to 1.0 mm/year. The likelihood of multi-fault rupture in the Torlesse Range has been characterised using paleoseismic trenching, a new structural model, and evaluation of existing paleoseismic data on the Porters Pass fault. Identification of overlapping of paleoseismic events in main Torlesse fault, flexural-slip faults and the Porters Pass fault in the Torlesse Range shows the possibility of distinct or multi-fault rupture on the Torlesse fault. The structural connectivity of the faults in the Torlesse zone forming a ‘flower structure’ supports the potential of multi-fault rupture. Multi-fault rupture modelling carried out in the area shows a high probability of rupture in the Porters Pass fault and Esk fault which also supports the co-rupture probability of faults in the region. This study offers a new understanding of the chronology, slip distribution, rupture characteristics and possible structural and kinematic relationship of Lake Heron fault and Torlesse fault in the South Island, New Zealand.
This thesis documents the development and demonstration of an assessment method for analysing earthquake-related damage to concrete waste water gravity pipes in Christchurch, New Zealand, following the 2010-2011 Canterbury Earthquake Sequence (CES). The method is intended to be internationally adaptable to assist territorial local authorities with improving lifelines infrastructure disaster impact assessment and improvements in resilience. This is achieved through the provision of high-resolution, localised damage data, which demonstrate earthquake impacts along the pipe length. The insights gained will assist decision making and the prioritisation of resources following earthquake events to quickly and efficiently restore network function and reduce community impacts. The method involved obtaining a selection of 55 reinforced concrete gravity waste water pipes with available Closed-Circuit Television (CCTV) inspection footage filmed before and after the CES. The pipes were assessed by reviewing the recordings, and damage was mapped to the nearest metre along the pipe length using Geographic Information Systems. An established, systematic coding process was used for reporting the nature and severity of the observed damage, and to differentiate between pre-existing and new damage resulting from the CES. The damage items were overlaid with geospatial data such as Light Detection and Ranging (LiDAR)-derived ground deformation data, Liquefaction Resistance Index data and seismic ground motion data (Peak Ground acceleration and Peak Ground Velocity) to identify potential relationships between these parameters and pipe performance. Initial assessment outcomes for the pipe selection revealed that main pipe joints and lateral connections were more vulnerable than the pipe body during a seismic event. Smaller diameter pipes may also be more vulnerable than larger pipes during a seismic event. Obvious differential ground movement resulted in increased local damage observations in many cases, however this was not obvious for all pipes. Pipes with older installation ages exhibited more overall damage prior to a seismic event, which is likely attributable to increased chemical and biological deterioration. However, no evidence was found relating pipe age to performance during a seismic event. No evidence was found linking levels of pre-CES damage in a pipe with subsequent seismic performance, and seismic performance with liquefaction resistance or magnitude of seismic ground motion. The results reported are of limited application due to the small demonstration sample size, but reveal the additional level of detail and insight possible using the method presented in this thesis over existing assessment methods, especially in relation to high resolution variations along the length of the pipe such as localised ground deformations evidenced by LiDAR. The results may be improved by studying a larger and more diverse sample pool, automating data collection and input processes in order to improve efficiency and consider additional input such as pipe dip and cumulative damage over a large distance. The method is dependent on comprehensive and accurate pre-event CCTV assessments and LIDAR data so that post-event data could be compared. It is proposed that local territorial authorities should prioritise acquiring this information as a first important step towards improving the seismic resilience of a gravity waste water pipe network.
This thesis documents the development and demonstration of an assessment method for analysing earthquake-related damage to concrete waste water gravity pipes in Christchurch, New Zealand, following the 2010-2011 Canterbury Earthquake Sequence (CES). The method is intended to be internationally adaptable to assist territorial local authorities with improving lifelines infrastructure disaster impact assessment and improvements in resilience. This is achieved through the provision of high-resolution, localised damage data, which demonstrate earthquake impacts along the pipe length. The insights gained will assist decision making and the prioritisation of resources following earthquake events to quickly and efficiently restore network function and reduce community impacts. The method involved obtaining a selection of 55 reinforced concrete gravity waste water pipes with available Closed-Circuit Television (CCTV) inspection footage filmed before and after the CES. The pipes were assessed by reviewing the recordings, and damage was mapped to the nearest metre along the pipe length using Geographic Information Systems. An established, systematic coding process was used for reporting the nature and severity of the observed damage, and to differentiate between pre-existing and new damage resulting from the CES. The damage items were overlaid with geospatial data such as Light Detection and Ranging (LiDAR)-derived ground deformation data, Liquefaction Resistance Index data and seismic ground motion data (Peak Ground acceleration and Peak Ground Velocity) to identify potential relationships between these parameters and pipe performance. Initial assessment outcomes for the pipe selection revealed that main pipe joints and lateral connections were more vulnerable than the pipe body during a seismic event. Smaller diameter pipes may also be more vulnerable than larger pipes during a seismic event. Obvious differential ground movement resulted in increased local damage observations in many cases, however this was not obvious for all pipes. Pipes with older installation ages exhibited more overall damage prior to a seismic event, which is likely attributable to increased chemical and biological deterioration. However, no evidence was found relating pipe age to performance during a seismic event. No evidence was found linking levels of pre-CES damage in a pipe with subsequent seismic performance, and seismic performance with liquefaction resistance or magnitude of seismic ground motion. The results reported are of limited application due to the small demonstration sample size, but reveal the additional level of detail and insight possible using the method presented in this thesis over existing assessment methods, especially in relation to high resolution variations along the length of the pipe such as localised ground deformations evidenced by LiDAR. The results may be improved by studying a larger and more diverse sample pool, automating data collection and input processes in order to improve efficiency and consider additional input such as pipe dip and cumulative damage over a large distance. The method is dependent on comprehensive and accurate pre-event CCTV assessments and LIDAR data so that post-event data could be compared. It is proposed that local territorial authorities should prioritise acquiring this information as a first important step towards improving the seismic resilience of a gravity waste water pipe network.
In the period between September 2010 and December 2011, Christchurch (New Zealand) and its surroundings were hit by a series of strong earthquakes including six significant events, all generated by local faults in proximity to the city: 4 September 2010 (Mw=7.1), 22 February 2011 (Mw=6.2), 13 June 2011 (Mw=5.3 and Mw=6.0) and 23 December 2011 (M=5.8 and (M=5.9) earthquakes. As shown in Figure 1, the causative faults of the earthquakes were very close to or within the city boundaries thus generating very strong ground motions and causing tremendous damage throughout the city. Christchurch is shown as a lighter colour area, and its Central Business District (CBD) is marked with a white square area in the figure. Note that the sequence of earthquakes started to the west of the city and then propagated to the south, south-east and east of the city through a set of separate but apparently interacting faults. Because of their strength and proximity to the city, the earthquakes caused tremendous physical damage and impacts on the people, natural and built environments of Christchurch. The 22 February 2011 earthquake was particularly devastating. The ground motions generated by this earthquake were intense and in many parts of Christchurch substantially above the ground motions used to design the buildings in Christchurch. The earthquake caused 182 fatalities, collapse of two multi-storey reinforced concrete buildings, collapse or partial collapse of many unreinforced masonry structures including the historic Christchurch Cathedral. The Central Business District (CBD) of Christchurch, which is the central heart of the city just east of Hagley Park, was practically lost with majority of its 3,000 buildings being damaged beyond repair. Widespread liquefaction in the suburbs of Christchurch, as well as rock falls and slope/cliff instabilities in the Port Hills affected tens of thousands of residential buildings and properties, and shattered the lifelines and infrastructure over approximately one third of the city area. The total economic loss caused by the 2010-2011 Christchurch earthquakes is currently estimated to be in the range between 25 and 30 billion NZ dollars (or 15% to 18% of New Zealand’s GDP). After each major earthquake, comprehensive field investigations and inspections were conducted to document the liquefaction-induced land damage, lateral spreading displacements and their impacts on buildings and infrastructure. In addition, the ground motions produced by the earthquakes were recorded by approximately 15 strong motion stations within (close to) the city boundaries providing and impressive wealth of data, records and observations of the performance of ground and various types of structures during this unusual sequence of strong local earthquakes affecting a city. This paper discusses the liquefaction in residential areas and focuses on its impacts on dwellings (residential houses) and potable water system in the Christchurch suburbs. The ground conditions of Christchurch including the depositional history of soils, their composition, age and groundwater regime are first discussed. Detailed liquefaction maps illustrating the extent and severity of liquefaction across Christchurch triggered by the sequence of earthquakes including multiple episodes of severe re-liquefaction are next presented. Characteristic liquefaction-induced damage to residential houses is then described focussing on the performance of typical house foundations in areas affected by liquefaction. Liquefaction impacts on the potable water system of Christchurch is also briefly summarized including correlation between the damage to the system, liquefaction severity, and the performance of different pipe materials. Finally, the characteristics of Christchurch liquefaction and its impacts on built environment are discussed in relation to the liquefaction-induced damage in Japan during the 11 March 2011 Great East Japan Earthquake.
