Numerical Study on the Role of Basin Geometry and Kinematic Seismic Source in 3D Ground Motion Simulation of the 22 February 2011 Mw 6.2 Christchurch Earthquake

Abstract

Almost six months after the MW 7.1 Darfield (Canterbury) earthquake, on 22 February 2011 at 12:51 p.m. (local time), an MW 6.2 earthquake struck the city and suburbs of Christchurch—the largest city on the South Island of New Zealand, with about 400,000 inhabitants. The Christchurch earthquake can be considered one of the greatest natural disasters recorded in New Zealand. The death toll was more than 180, with around 2,000 people injured, and structures already weakened by the Darfield event and its aftershocks were badly affected (Cubrinovski and Green 2010; Tonkin and Taylor Ltd. 2010; Kam et al. 2011). The earthquake was generated by an oblique thrust fault located between the Australian and Pacific plates, within about 6 km of the city center. It is worth recalling that prior to the Darfield event there was no surface evidence of the fault that generated the Christchurch earthquake on February 2011, nor of the Greendale fault, recognized as responsible for the September 2010 earthquake (Quigley et al. 2010). During the last decade a set of seismic surveys across the Canterbury Plains had been carried out (Green et al. 2010), but they did not reveal any convincing evidence of the Greendale fault and there was no clear indication that a major earthquake was imminent in this particular region. Beyond the effects and the consequences of the seismic event, the attention of the scientific community was drawn to two aspects that had a primary role in the Christchurch earthquake: 1) the extremely severe, strong ground shaking observed, especially on the vertical component; and 2) the widespread liquefaction phenomena across the city (Cubrinovski and Green 2010; Green et al. 2011, page 927 of this issue). Between September 2010 and June 2011 the Canterbury area experienced three major earthquakes with M …