Liquefaction and strong motion during the 2010-2011 Canterbury earthquake sequence

Monday, 15 December 2014
Michael Chamberlain1, Chi-Yuen Wang1, Douglas Scott Dreger1 and Simon Cox2, (1)University of California Berkeley, Berkeley, CA, United States, (2)GNS Science-Institute of Geological and Nuclear Sciences Ltd, Lower Hutt, New Zealand
Liquefaction is a major seismic hazard for engineered structures; thus improved ability to predict the potential for liquefaction in seismically active regions is badly needed. The 2010 Mw 7.1 Darfield event and its associated aftershock sequence caused numerous occurrences of liquefaction in the Canterbury region of New Zealand, providing an excellent opportunity to study the occurrence of liquefaction in coastal plains near an active mountain belt. In this study we utilize strong motion data from over 100 stations in the New Zealand region and examine a number of major liquefaction events associated with the Canterbury earthquake sequence. These data are used to construct empirical attenuation relationships of ground motion as functions of hypocentral distance. The attenuation relationships so derived for the Canterbury region are similar to those developed for Southern California. This similarity suggests some generality of ground motion attenuation in sedimentary basins, even between geographically disparate regions. These relationships are used to estimate the seismic energy density at each liquefaction site in the Canterbury region, which is compared with a global database of liquefaction occurrences. Some liquefaction sites in the Canterbury region experienced seismic energy densities near the lower threshold for liquefaction established for the global dataset, suggesting high sensitivity to liquefaction.