Spatial evaluation of liquefaction potential in Christchurch following the 2010/2011 Canterbury earthquakes

Abstract

Widespread damage as a result of liquefaction was observed in the Canterbury region following the 2010 Darfield earthquake and the 2011 Christchurch earthquake. To quantify the liquefaction risk in some areas associated with these two events, strong motion records and available boring data were used to produce maps showing distributions of liquefaction potential indices (LPI). It was found that for both events, the distributions of LPI values agree reasonably well with the observed severity of damage. The increased peak accelerations during the February 2011 event along with the elevated water table resulted in more severe damage in eastern Christchurch than during the 2010 earthquake, while the lower shaking intensity in the Waimakariri region led to a severe but more localized liquefaction. In cases where the calculated LPI and observed damage did not agree, the occurrence of lateral spreading and the thickness of the surface crust appear to be the main reasons. Finally, through analysis of boring data, the role of the surface crust in liquefaction manifestation was analyzed.