Surface rupture during the 2010 Mw 7.1 Darfield (Canterbury) earthquake: Implications for fault rupture dynamics and seismic-hazard analysis

The September 2010 M-w 7.1 Darfield (Canterbury) earthquake in New Zealand is one of the best-recorded earthquakes of this magnitude. The earthquake occurred on a previously unidentified fault system and generated a 29.5 +/- 0.5-km-long surface rupture across a low-relief agricultural landscape. High-accuracy measurements of coseismic displacements were obtained at over 100 localities along the Greendale fault. Maximum net displacement (D-max) (5.3 +/- 0.5 m) and average net displacement (D-avg) (2.5 +/- 0.1 m) are anomalously large for an earthquake of this M-w.D-max/surface rupture length (SRL) and D-avg/SRL ratios are among the largest ever recorded for a continental strike-slip earthquake. "Geologically derived" estimates of moment magnitude (M-w(G)) are less than the seismologically derived M-w, derived using widely employed SRL-M-w scaling regressions. M-w(G) is greater than M-w using D-max- and D-avg-M-w regressions. The "geologically derived" static stress drop of 13.9 +/- 3.7 MPa provides a context with which to compare this earthquake rupture to interplate and intraplate ruptures of similar M-w. This data set provides fundamental information on fault rupture processes relevant to seismic-hazard modeling in this region and analogous settings globally.