Evolution of the 2010–2012 Canterbury earthquake sequence

Abstract

We present an overview of the evolution of the 2010–2012 Canterbury earthquake sequence, summarising the findings from a broad range of studies on the larger earthquakes. The sequence began with the M W7.1 Darfield earthquake on 4 September 2010 and continued in a series of aftershocks through the remainder of 2010 and early 2011, before the devastating M W6.2 Christchurch earthquake of 22 February 2011 which resulted in 185 deaths, more than NZ$11 billion of damage and extensive liquefaction. Another significant M W6.0 aftershock occurred on 13 June 2011 causing more liquefaction and damage in the eastern hill suburbs, while further activity, including events of M W5.8 and M W5.9, occurred offshore from Christchurch in December 2011. Only the Darfield earthquake resulted in visible surface faulting, with a c. 30-km-long east–west-trending surface rupture exhibiting horizontal displacements of up to 5 m. The earthquakes displayed a variety of strike-slip and reverse faulting mechanisms. The entire Canterbury earthquake sequence has been well recorded by an extensive permanent seismograph network (GeoNet) and additional temporary instruments, providing a rare set of near-source recordings of high ground accelerations and broadband waveforms that will influence earthquake studies in New Zealand and overseas for decades to come.