Comparison of liquefaction Features observed during the 2010 and 2011 Canterbury earthquakes

Abstract

On 4 September 2010, a magnitude M = 7.1 earthquake struck the Canterbury region on the South Island of New Zealand. The epicenter of the earthquake was located near Darfield, about 40 km west of the central business district (CBD) of the city of Christchurch and at a depth of about 10 km. Extensive damage was inflicted on lifelines and residential houses due to widespread liquefaction and lateral spreading in areas close to major streams, rivers, and wetlands throughout the city of Christchurch and the town of Kaiapoi. In the months following the Darfield M 7.1 earthquake, numerous aftershocks were felt across the city. Almost six months after the Darfield mainshock, on 22 February 2011, the Canterbury region was hit by a magnitude M = 6.3 earthquake. The epicenter was located near Lyttelton, only 6 km to the southeast of the Christchurch CBD and at a depth of 5 km. In spite of its smaller magnitude, this earthquake resulted in more damage to pipeline networks, transport facilities, residential houses/properties, and multistory buildings in the CBD than the September 2010 event, mainly because of the short distance to the city and the shallower depth. Although there were no casualties after the 2010 Darfield earthquake, which is sort of a miracle considering the magnitude of the earthquake, the 2011 Christchurch earthquake resulted in a significant number of casualties due to the collapse of multistory buildings and unreinforced masonry structures in the Christchurch city center. As of 1 June 2011, 181 casualties were reported (New Zealand Police; http://www.police.govt.nz/list-deceased). While it is extremely regrettable that the 2011 Christchurch earthquake resulted in significant casualties, engineers and seismologists now have a hard-to-find opportunity to learn the response of ground and structures to two large-scale earthquakes that occurred less than six months apart. From a geotechnical …