Factors Contributing to Multi-Segment Rupture in the 2010 M7.1 Darfield, New Zealand, Earthquake

We use dynamic prescribed slip and spontaneous rupture modeling to examine the factors contributing to multi-segment rupture in the 2010 M7.1 Darfield, New Zealand, earthquake. The simulations build upon the geodetic inversion of static slip and fault geometry by Beavan et al. (2012). We find that dynamic stress changes and the orientation of the faults with respect to the regional stress field as well as the strike-slip/reverse faulting regime create favorable conditions for triggering of the main rupture on the Greendale fault from rupture initiating on the Charing Cross fault. Orientation of the regional stress field and the faulting regime may have also contributed to triggering of rupture on a few other small faults in which geodetic inversions, e.g. Beavan et al. (2012), image minor slip. These faults include the Hororata reverse fault west of the epicenter and an oblique fault northwest of the epicenter. However, owing to the complexity of the seismic coda, recorded waveforms provide relatively poor constraints on whether coseismic slip and dynamic triggering occurred late in the rupture process on these faults with relatively minor slip.