Abstract

The September 2010 Mw 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 (Dmax) (5.3 ± 0.5 m) and average net displacement (Davg) (2.5 ± 0.1 m) are anomalously large for an earthquake of this Mw. Dmax / surface rupture length (SRL) and Davg/SRL ratios are among the largest ever recorded for a continental strike-slip earthquake. “Geologically derived” estimates of moment magnitude (MwG) are less than the seismologically derived Mw, derived using widely employed SRL-Mw scaling regressions. MwG is greater than Mw using Dmax- and Davg-Mw 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 Mw. This data set provides fundamental information on fault rupture processes relevant to seismic-hazard modeling in this region and analogous settings globally.

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