The Liquefaction Model
The 2010 M7.1 Darfield earthquake in New Zealand started a sequence of events – the Canterbury Earthquake Sequence (CES), that propagated eastward in the Canterbury region over several years. Since the City of Christchurch is built on alluvial sediments where the water table is very shallow, several of the larger events created widespread liquefaction within the city and surrounding areas. Such ground deformations caused a significant number of buildings with shallow foundations to settle, tilt and deform.
Prior to these New Zealand earthquakes, liquefaction was observed but not on this scale in a built-up area in a developed country. As in previous well-studied liquefaction events (e.g. 1964 Niigata) this was a unique opportunity to examine liquefaction severity and building responses. Christchurch was referred to as a “liquefaction laboratory” with the multiple events causing different levels of shaking across the city. However, we had not previously seen suburbs of insured buildings damaged by liquefaction.Continue reading