The influence of near-fault motions on liquefaction triggering during the Canterbury earthquake sequence

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Publisher
University of Canterbury. Civil and Natural Resources Engineering
Journal Title
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Date
2013
Authors
Carter, L.
Green, R.A.
Bradley, Brendon
Cubrinovski, M.
Abstract

The objective of this study is to examine the influence of near-fault motions on liquefaction triggering in Christchurch and neighboring towns during the 2010-2011 Canterbury earthquake sequence (CES). The CES began with the 4 September 2010, Mw7.1 Darfield earthquake and included up to ten events that triggered liquefaction. However, most notably, widespread liquefaction was induced by the Darfield earthquake and the Mw6.2, 22 February 2011 Christchurch earthquake. Of particular relevance to this study is the forward directivity effects that were prevalent in the motions recorded during the Darfield earthquake, and to a much lesser extent, during the Christchurch earthquake. A 2D variant of the Richart-Newmark fatigue theory was used to compute the equivalent number of cycles (neq) for the ground motions, where volumetric strain was used as the damage metric. This study is unique because it considers the contribution and phasing of both the fault-normal and fault-parallel components of motion on neq and the magnitude scaling factor (MSF). It was found that when the fault-normal and fault-parallel motions were treated individually, the former yielded a lower neq than the latter. Additionally, when the combined effects of fault-normal and fault-parallel components were considered, it was found that the MSF were higher than those commonly used. This implies that motions containing near-fault effects are less demanding on the soil than motions that do not. This may be one of several factors that resulted in less severe liquefaction occurring during the Darfield earthquake than the Christchurch earthquake.

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Citation
Carter, L., Green, R.A., Bradley, B.A., Cubrinovski, M. (2013) The influence of near-fault motions on liquefaction triggering during the Canterbury earthquake sequence. Auckland, New Zealand: New Zealand – Japan Workshop on Soil Liquefaction during Recent Large-scale Earthquakes, 2-3 Dec 2013.
Keywords
Canterbury earthquake sequence, liquefaction, near-fault, rupture directivity
Ngā upoko tukutuku/Māori subject headings
ANZSRC fields of research
Fields of Research::40 - Engineering::4005 - Civil engineering::400506 - Earthquake engineering
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