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Research papers, University of Canterbury Library

This study contains an evaluation of the seismic hazard associated with the Springbank Fault, a blind structure discovered in 1998 close to Christchurch. The assessment of the seismic hazard is approached as a deterministic process in which it is necessary to establish: 1) fault characteristics; 2) the maximum earthquake that the fault is capable of producing and 3) ground motions estimations. Due to the blind nature of the fault, conventional techniques used to establish the basic fault characteristics for seismic hazard assessments could not be applied. Alternative methods are used including global positioning system (GPS) surveys, morphometric analyses along rivers, shallow seismic reflection surveys and computer modelling. These were supplemented by using multiple empirical equations relating fault attributes to earthquake magnitude, and attenuation relationships to estimate ground motions in the near-fault zone. The analyses indicated that the Springbank Fault is a reverse structure located approximately 30 km to the northwest of Christchurch, along a strike length of approximately 16 km between the Eyre and Ashley River. The fault does not reach the surface, buy it is associated with a broad anticline whose maximum topographic expression offers close to the mid-length of the fault. Two other reverse faults, the Eyrewell and Sefton Faults, are inferred in the study area. These faults, together with the Springbank and Hororata Faults and interpreted as part of a sys of trust/reverse faults propagating from a decollement located at mid-crustal depths of approximately 14 km beneath the Canterbury Plains Within this fault system, the Springbank Fault is considered to behave in a seismically independent way, with a fault slip rate of ~0.2 mm/yr, and the capacity of producing a reverse-slip earthquake of moment magnitude ~6.4, with an earthquake recurrence of 3,000 years. An earthquake of the above characteristics represents a significant seismic hazard for various urban centres in the near-fault zone including Christchurch, Rangiora, Oxford, Amberley, Kaiapoi, Darfield, Rollestion and Cust. Estimated peak ground accelerations for these towns range between 0.14 g to 0.5 g.

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

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.

Research papers, University of Canterbury Library

On 4 September 2010, a magnitude Mw 7.1 earthquake struck the Canterbury region on the South Island of New Zealand. The epicentre of the earthquake was located in the Darfield area about 40 km west of the city of Christchurch. Extensive damage occurred to unreinforced masonry buildings throughout the region during the mainshock and subsequent large aftershocks. Particularly extensive damage was inflicted to lifelines and residential houses due to widespread liquefaction and lateral spreading in areas close to major streams, rivers and wetlands throughout Christchurch and Kaiapoi. Despite the severe damage to infrastructure and residential houses, fortunately, no deaths occurred and only two injuries were reported in this earthquake. From an engineering viewpoint, one may argue that the most significant aspects of the 2010 Darfield Earthquake were geotechnical in nature, with liquefaction and lateral spreading being the principal culprits for the inflicted damage. Following the earthquake, a geotechnical reconnaissance was conducted over a period of six days (10–15 September 2010) by a team of geotechnical/earthquake engineers and geologists from New Zealand and USA (GEER team: Geo-engineering Extreme Event Reconnaissance). JGS (Japanese Geotechnical Society) members from Japan also participated in the reconnaissance team from 13 to 15 September 2010. The NZ, GEER and JGS members worked as one team and shared resources, information and logistics in order to conduct thorough and most efficient reconnaissance covering a large area over a very limited time period. This report summarises the key evidence and findings from the reconnaissance.

Research papers, University of Canterbury Library

This study provides an initial examination of source parameter uncertainty in a New Zealand ground motion simulation model, by simulating multiple event realisations with perturbed source parameters. Small magnitude events in Canterbury have been selected for this study due to the small number of source input parameters, the wealth of recorded data, and the lack of appreciable off-fault non-linear effects. Which provides greater opportunity to identify systematic source, path and site effects, required to robustly investigate the causes of uncertainty.

Research papers, University of Canterbury Library

In the last two decades, New Zealand (NZ) has experienced significant earthquakes, including the 2010 M 7.2 Darfield, 2011 M 6.2 Christchurch, and 2016 M 7.8 Kaikōura events. Amongst these large events, tens of thousands of smaller earthquakes have occurred. While previous event and ground-motion databases have analyzed these events, many events below M 4 have gone undetected. The goal of this study is to expand on previous databases, particularly for small magnitude (M<4) and low-amplitude ground motions. This new database enables a greater understanding of regional variations within NZ and contributes to the validity of internationally developed ground-motion models. The database includes event locations and magnitude estimates with uncertainty considerations, and tectonic type assessed in a hierarchical manner. Ground motions are extracted from the GeoNet FDSN server and assessed for quality using a neural network classification approach. A deep neural network approach is also utilized for picking P and S phases for determination of event hypocentres. Relative hypocentres are further improved by double-difference relocation and will contribute toward developing shallow (< 50 km) seismic tomography models. Analysis of the resulting database is compared with previous studies for discussion of implications toward national hazard prediction models.

Research papers, University of Canterbury Library

This paper presents an examination of ground motion observations from 20 near-source strong motion stations during the most significant 10 events in the 2010-2011 Canterbury earthquake to examine region-specific systematic effects based on relaxing the conventional ergodic assumption. On the basis of similar site-to-site residuals, surfical geology, and geographical proximity, 15 of the 20 stations are grouped into four sub-regions: the Central Business District; and Western, Eastern, and Northern suburbs. Mean site-to-site residuals for these sub-regions then allows for the possibility of non-ergodic ground motion prediction over these sub-regions of Canterbury, rather than only at strong motion station locations. The ratio of the total non-ergodic vs. ergodic standard deviation is found to be, on average, consistent with previous studies, however it is emphasized that on a site-by-site basis the non-ergodic standard deviation can easily vary by ±20%.

Research papers, The University of Auckland Library

The city of Christchurch has experienced over 10,000 aftershocks since the 4th of September 2010 earthquake of which approximately 50 have been greater than magnitude 5. The damage caused to URM buildings in Christchurch over this sequence of earthquakes has been well documented. Due to the similarity in age and construction of URM buildings in Adelaide, South Australia and Christchurch (they are sister cities, of similar age and heritage), an investigation was conducted to learn lessons for Adelaide based on the Christchurch experience. To this end, the number of URM buildings in the central business districts of both cities, the extent of seismic strengthening that exists in both cities, and the relative earthquake hazards for both cities were considered. This paper will report on these findings and recommend strategies that the city of Adelaide could consider to significantly reduce the seismic risk posed by URM buildings in future earthquake.

Videos, UC QuakeStudies

A video of a panel discussion at the 2016 Seismics in the City Conference. The panel is titled, "Engaging: Generating Community Input and Feedback".Leanne Curtis of Breakthrough Services, Evan Smith, Programme Manager of Eastern Vision, and André Lovatt, CEO of the Arts Centre, present case studies.The theme of the panel reads, "'Regenerate Christchurch must and will engage with the community around what will be done' (André Lovatt, Chair, Regenerate Christchurch). Learning from the past by tapping the wisdom of communities and applying the lessons to the future as we shape the new city."

Videos, UC QuakeStudies

A video of a presentation by André Lovatt, Chair of Regenerate Christchurch, during a panel at the 2016 Seismics in the City Conference. The panel has three themes:A City on the Move: Collaboration and Regeneration: "'Christchurch is now moving rapidly from the recovery phase into a regeneration stage with Central and Local Government working with the wider community, including the business community to ensure we get optimal outcomes for greater Christchurch' (CECC)."Looking Back: Remembering and Learning: "What are the milestones? What are the millstones? What have we learnt? What have we applied?"Looking Forward: Visioning and Building: "What do we aspire to? What are the roadblocks? What is the way forward?"

Videos, UC QuakeStudies

A video of a presentation by Hugh Cowan, General Manager of Reinsurance, Research and Education at EQC, during a panel at the 2016 Seismics in the City Conference. The panel has three themes:A City on the Move: Collaboration and Regeneration: "'Christchurch is now moving rapidly from the recovery phase into a regeneration stage with Central and Local Government working with the wider community, including the business community to ensure we get optimal outcomes for greater Christchurch' (CECC)."Looking Back: Remembering and Learning: "What are the milestones? What are the millstones? What have we learnt? What have we applied?"Looking Forward: Visioning and Building: "What do we aspire to? What are the roadblocks? What is the way forward?"

Videos, UC QuakeStudies

A video of a presentation by Peter Townsend, CEO of the Canterbury Employers' Chamber of Commerce, during a panel at the 2016 Seismics in the City Conference. The panel has three themes:A City on the Move: Collaboration and Regeneration: "'Christchurch is now moving rapidly from the recovery phase into a regeneration stage with Central and Local Government working with the wider community, including the business community to ensure we get optimal outcomes for greater Christchurch' (CECC)."Looking Back: Remembering and Learning: "What are the milestones? What are the millstones? What have we learnt? What have we applied?"Looking Forward: Visioning and Building: "What do we aspire to? What are the roadblocks? What is the way forward?"

Videos, UC QuakeStudies

A video of a presentation by Hon. Lianne Dalziel, Mayor of Christchurch, during a panel at the 2016 Seismics in the City Conference. The panel has three themes:A City on the Move: Collaboration and Regeneration: "'Christchurch is now moving rapidly from the recovery phase into a regeneration stage with Central and Local Government working with the wider community, including the business community to ensure we get optimal outcomes for greater Christchurch' (CECC)."Looking Back: Remembering and Learning: "What are the milestones? What are the millstones? What have we learnt? What have we applied?"Looking Forward: Visioning and Building: "What do we aspire to? What are the roadblocks? What is the way forward?"

Videos, UC QuakeStudies

A video of a presentation by Hon. Nicky Wagner, Associate Minister for Canterbury Earthquake Recovery, during a panel at the 2016 Seismics in the City Conference. The panel has three themes:A City on the Move: Collaboration and Regeneration: "'Christchurch is now moving rapidly from the recovery phase into a regeneration stage with Central and Local Government working with the wider community, including the business community to ensure we get optimal outcomes for greater Christchurch' (CECC)."Looking Back: Remembering and Learning: "What are the milestones? What are the millstones? What have we learnt? What have we applied?"Looking Forward: Visioning and Building: "What do we aspire to? What are the roadblocks? What is the way forward?"

Research papers, University of Canterbury Library

The latest two great earthquake sequences; 2010- 2011 Canterbury Earthquake and 2016 Kaikoura Earthquake, necessitate a better understanding of the New Zealand seismic hazard condition for new building design and detailed assessment of existing buildings. It is important to note, however, that the New Zealand seismic hazard map in NZS 1170.5.2004 is generalised in effort to cover all of New Zealand and limited to a earthquake database prior to 2001. This is “common” that site-specific studies typically provide spectral accelerations different to those shown on the national map (Z values in NZS 1170.5:2004); and sometimes even lower. Moreover, Section 5.2 of Module 1 of the Earthquake Geotechnical Engineering Practice series provide the guidelines to perform site- specific studies.

Videos, UC QuakeStudies

A video of an address by Alex Cutler, CEO of the New Zealand Green Building Council, at the 2014 Seismics and the City forum. This talk was part of the Building Communities section and explored the extent to which the new city core will be a 'government-flavoured doughnut', the key issues with this concept, and the possible solutions.

Research papers, The University of Auckland Library

The paper proposes a simple method for quick post-earthquake assessment of damage and condition of a stock of bridges in a transportation network using seismic data recorded by a strong motion array. The first part of the paper is concerned with using existing free field strong motion recorders to predict peak ground acceleration (PGA) at an arbitrary bridge site. Two methods are developed using artificial neural networks (a single network and a committee of neural networks) considering influential parameters, such as seismic magnitude, hypocentral depth and epicentral distance. The efficiency of the proposed method is explored using actual strong motion records from the devastating 2010 Darfield and 2011 Christchurch earthquakes in New Zealand. In the second part, two simple ideas are outlined how to infer the likely damage to a bridge using either the predicted PGA and seismic design spectrum, or a broader set of seismic metrics, structural parameters and damage indices.

Research papers, University of Canterbury Library

There is an increasing recognition that the seismic performance of buildings will be affected by the behaviour of both structural and non-structural elements. In light of this, work has been progressing at the University of Canterbury to develop guidelines for the seismic assessment of commercial glazing systems. This paper reviews the seismic assessment guidelines prescribed in Section C10 of the MBIE building assessment guidelines. Subsequently, the C10 approach is used to assess the drift capacity of a number of glazing units recently tested at the University of Canterbury. Comparing the predicted and observed drift capacities, it would appear that the C10 guidelines may lead to nonconservative estimates of drift capacity. Furthermore, the experimental results indicate that watertightness may be lost at very low drift demands, suggesting that guidance for the assessment of serviceability performance would also be beneficial. As such, it is proposed that improved guidance be provided to assist engineers in considering the possible impact that glazing could have on the structural response of a building in a large earthquake.

Research papers, The University of Auckland Library

The current seismic design practice for reinforced concrete (RC) walls has been drawn into question following the unsatisfactory performance of several RC wall buildings during the Canterbury earthquakes. An overview of current research being undertaken at the University of Auckland into the seismic behaviour of RC walls is presented. The main objectives of this research project are to understand the observed performance of RC walls in Christchurch, quantify the seismic loads on RC walls, and developed improved design procedures for RC walls that will assist in revisions to the New Zealand Concrete Structures Standard. A database summarising the performance of RC wall buildings in the Christchurch CBD was collated to identify damage modes and case-study buildings. A detailed investigation is underway to verify the seismic performance of lightly reinforced concrete walls and initial numerical modeling and small-scale tests are presented in addition to details of planned experimental tests of RC walls. Numerical modelling is being used to understand the potential influence that interactions between walls and other structural elements have on the seismic response of buildings and the loads generated on RC walls. The results from finite element analysis of a severely damaged RC wall in Christchurch highlighted the effect that the floor diaphragms have on the distribution of shear stains in the wall.

Research papers, University of Canterbury Library

Nowadays the telecommunication systems’ performance has a substantial impact on our lifestyle. Their operationality becomes even more substantial in a post-disaster scenario when these services are used in civil protection and emergency plans, as well as for the restoration of all the other critical infrastructure. Despite the relevance of loss of functionality of telecommunication networks on seismic resilience, studies on their performance assessment are few in the literature. The telecommunication system is a distributed network made up of several components (i.e. ducts, utility holes, cabinets, major and local exchanges). Given that these networks cover a large geographical area, they can be easily subjected to the effects of a seismic event, either the ground shaking itself, or co-seismic events such as liquefaction and landslides. In this paper, an analysis of the data collected after the 2010-2011 Canterbury Earthquake Sequence (CES) and the 2016 Kaikoura Earthquake in New Zealand is conducted. Analysing these data, information gaps are critically identified regarding physical and functional failures of the telecommunication components, the timeline of repair/reconstruction activities and service recovery, geotechnical tests and land planning maps. Indeed, if these missing data were presented, they could aid the assessment of the seismic resilience. Thus, practical improvements in the post-disaster collection from both a network and organisational viewpoints are proposed through consultation of national and international researchers and highly experienced asset managers from Chorus. Finally, an outline of future studies which could guide towards a more resilient seismic performance of the telecommunication network is presented.

Research papers, University of Canterbury Library

Seismic isolation is an effective technology for significantly reducing damage to buildings and building contents. However, its application to light-frame wood buildings has so far been unable to overcome cost and technical barriers such as susceptibility to movement during high-wind loading. The precursor to research in the field of isolation of residential buildings was the 1994 Northridge Earthquake (6.7 MW) in the United States and the 1995 Kobe Earthquake (6.9 MW) in Japan. While only a small number of lives were lost in residential buildings in these events, the economic impact was significant with over half of earthquake recovery costs given to repair and reconstruction of residential building damage. A value case has been explored to highlight the benefits of seismically isolated residential buildings compared to a standard fixed-base dwellings for the Wellington region. Loss data generated by insurance claim information from the 2011 Christchurch Earthquake has been used by researchers to determine vulnerability functions for the current light-frame wood building stock. By further considering the loss attributed to drift and acceleration sensitive components, and a simplified single degree of freedom (SDOF) building model, a method for determining vulnerability functions for seismic isolated buildings was developed. Vulnerability functions were then applied directly in a loss assessment using the GNS developed software, RiskScape. Vulnerability was shown to dramatically reduce for isolated buildings compared to an equivalent fixed-base building and as a result, the monetary savings in a given earthquake scenario were significant. This work is expected to drive further interest for development of solutions for the seismic isolation of residential dwellings, of which one option is further considered and presented herein.

Research papers, University of Canterbury Library

The performance of buildings in recent New Zealand earthquakes (Canterbury, Seddon and Kaikōura), delivered stark lessons on seismic resilience. Most of our buildings, with a few notable exceptions, performed as our Codes intended them to, that is, to safeguard people from injury. Many buildings only suffered minor structural damage but were unable to be reused and occupied for significant periods of time due to the damage and failure of non-structural elements. This resulted in substantial economic losses and major disruptions to our businesses and communities. Research has attributed the damage to poor overall design coordination, inadequate or lack of seismic restraints for non structural elements and insufficient clearances between building components to cater for the interaction of non structural elements under seismic actions. Investigations have found a clear connection between the poor performance of non-structural elements and the issues causing pain in the industry (procurement methods, risk aversion, the lack of clear understanding of design and inspection responsibility and the need for better alignment of the design codes to enable a consistent integrated design approach). The challenge to improve the seismic performance of non structural elements in New Zealand is a complex one that cuts across a diverse construction industry. Adopting the key steps as recommended in this paper is expected to have significant co-benefits to the New Zealand construction industry, with improvements in productivity alongside reductions in costs and waste, as the rework which plagues the industry decreases.