Influence of Site Effects on Observed Ground Motions in the Wellington Region from the Mw 7.8 Kaikōura, New Zealand, Earthquake

Bradley, Brendon; Wotherspoon, Liam; Kaiser, Anna; Cox, Brady R.; Jeong, Seokho

doi:10.1785/0120170286

Cited by 29 publications

(18 citation statements)

References 30 publications

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“…Significant damage has been identified in and around the Wellington CBD basins, as shown in Brunsdon et al in Figure 2. This paper will not cover the tectonic setting, rupture, and ground performance -the details of which have been much explained by others [14][15][16][17] -except in so far as they relate directly to observed building behaviour.…”

Section: The Kaikōura Earthquakementioning

confidence: 99%

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Basin edge effects and damping

Ballagh¹,

Cattanach²

2019

BNZSEE

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The Kaikōura earthquake brought the concept of basin effects to the forefront of conversation about building in the Wellington CBD. Local exceedances of ULS design spectra were observed in many waterfront sites in the 1.5-2.5s period range. This, coupled with low yield levels and certain structural forms present in previous generations of building design, meant that significant damage occurred in many buildings around the Wellington waterfront.A primary cause for the high spectral accelerations was the geological structure of the Wellington CBD. This paper will focus on the behaviour of generic buildings in response to these particular ground motions and suggest how lessons from this can inform the design of future buildings. It uses the Kaikōura Earthquake as the centre point for discussions about the relationship between building behaviour on soft soils and the effects on this of different forms of damping. More broadly, the aim is to help spark debate in the earthquake engineering community on the question: What sorts of structures should we be building on soft soil sites?This paper has been written in the wake of a number of damaging earthquakes throughout New Zealand, and with the concurrent increase in sophistication and spread of tools for analysing the effects of the ground motions induced by these earthquakes. The genesis of the ideas presented herein was in analysis of many waterfront buildings following the Kaikoura earthquake, and the attempts, often in vain, to match modelled building behaviour-where small tweaks in assumptions could have a radical effect on results-with actual observed damagewhere cracks may have been seen in concrete or in partitions, but assessment of actual plastic strains reached in steel bars or beams was basically conjecture. This paper is broad in scope, therefore cannot possibly give each aspect the coverage of a series of papers which consider them in isolation and in detail. We nonetheless strongly believe that a holistic view of all topics is critical for design, and that the authors as 'front line' structural engineers are well positioned to present this. Sincere attempts have been made to justify our point of view with a strong basis in first principles, and backed by nonlinear time history analysis, or by reference to the work of others. We acknowledge that our beliefs are not shared by everyone and that some conclusions are provocative. It is neither the intent nor even the hope that we have the last word on this topic.

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Section: The Kaikōura Earthquakementioning

confidence: 99%

“…It has been noted that the basin effects can be expected to be repeatable -if perhaps not identical -across virtually all future earthquakes [14,23]. What can then be expected from a rupture of higher magnitude, longer and closer earthquake?…”

Section: Ultimate Limit Statementioning

confidence: 99%

Basin edge effects and damping

Ballagh¹,

Cattanach²

2019

BNZSEE

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“…Rupturing began on a fault near the small town of Waiau in North Canterbury [14], south-west and inland of the coastal community of Kaikōura, a popular tourism destination (Figure 1). The quake was shallow-approximately 15 km deep-but fast, the fault rupturing at a speed of 1.8 km/s (6450 km/h) [15]. The earthquake-officially the Kaikōura-Marlborough-Hurunui sequence to delineate all affected regions-ultimately included the rupture of 21 faults across a span of approximately 180 km 2 [16].…”

Section: Introductionmentioning

confidence: 99%

“…Compared to the same November-December period the previous year, domestic and international tourism expenditure in the region fell by 20%, a loss of over NZ$21 million [18]. Two-hundred kilometres to the north, the capital city of Wellington was also affected [15,19,20]. Major office buildings and commercial spaces were permanently damaged, others were closed temporarily to assess damage.…”

Section: Introductionmentioning

confidence: 99%

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Transformations for Resilient Rural Futures: The Case of Kaikōura, Aotearoa-New Zealand

2018

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On 14 November 2016, a magnitude (M w ) 7.8 earthquake struck the small coastal settlement of Kaikōura, Aotearoa-New Zealand. With an economy based on tourism, agriculture, and fishing, Kaikōura was immediately faced with significant logistical, economic, and social challenges caused by damage to critical infrastructure and lifelines, essential to its main industries. Massive landslips cut off road and rail access, stranding hundreds of tourists, and halting the collection, processing and distribution of agricultural products. At the coast, the seabed rose two metres, limiting harbour-access to high tide, with implications for whale watching tours and commercial fisheries. Throughout the region there was significant damage to homes, businesses, and farmland, leaving owners and residents facing an uncertain future. This paper uses qualitative case study analysis to explore post-quake transformations in a rural context. The aim is to gain insight into the distinctive dynamics of disaster response mechanisms, focusing on two initiatives that have emerged in direct response to the disaster. The first examines the ways in which agriculture, food harvesting, production and distribution are being reimagined with the potential to enhance regional food security. The second examines the rescaling of power in decision-making processes following the disaster, specifically examining the ways in which rural actors are leveraging networks to meet their needs and the consequences of that repositioning on rural (and national) governance arrangements. In these and other ways, the local economy is being revitalised, and regional resilience enhanced through diversification, capitalising not on the disaster but the region's natural, social, and cultural capital. Drawing on insights and experience of local stakeholders, policy-and decision-makers, and community representatives we highlight the diverse ways in which these endeavours are an attempt to create something new, revealing also the barriers which needed to be overcome to reshape local livelihoods. Results reveal that the process of transformation as part of rural recovery must be grounded in the lived reality of local residents and their understanding of place, incorporating and building on regional social, environmental, and economic characteristics. In this, the need to respond rapidly to realise opportunities must be balanced with the community-centric approach, with greater recognition given to the contested nature of the decisions to be made. Insights from the case examples can inform preparedness and recovery planning elsewhere, and provide a rich, real-time example of the ways in which disasters can create opportunities for reimagining resilient futures.

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Nonstationary spatial correlation in New Zealand strong ground‐motion data

Chen

Bradley

Baker

2021

Earthq Engng Struct Dyn

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This paper presents new techniques for quantifying nonstationary spatial variations in strong ground motion, using data from recent well‐recorded earthquakes in New Zealand. The data set is unique in that many recording stations are relatively densely spaced, and multiple strong ground motions have been recorded at the same stations. This allows calculation of site‐specific and region‐specific correlations in ground‐motion amplitude for Wellington and Christchurch, and the results are compared to a model assuming stationary correlations at all locations. Strong nonstationarity in spatial correlation is observed in the Wellington and Christchurch regions. Heterogeneous geologic conditions appear to be associated with the nonstationary spatial correlation. Several factors influencing nonstationary spatial correlation were studied: (a) site‐specific residuals indicate deviation of correlation from a stationary model; (b) most earthquakes have no systematic effect on spatial correlations and there is no indication of a trend in correlations with magnitude; (c) rupture complexity is related to the variation of spatial correlations in ground‐motion residuals; (d) variation of site‐specific correlations cannot be resolved by using VS,30 terms in Ground‐Motion Models. The nonstationary correlation approach provides an opportunity to incorporate the site‐specific effects in future correlation models.

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Influence of Site Effects on Observed Ground Motions in the Wellington Region from the Mw 7.8 Kaikōura, New Zealand, Earthquake

Cited by 29 publications

References 30 publications

Basin edge effects and damping

Basin edge effects and damping

Transformations for Resilient Rural Futures: The Case of Kaikōura, Aotearoa-New Zealand

Nonstationary spatial correlation in New Zealand strong ground‐motion data

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