The 2010 Darfield Mw7.1 earthquake occurred on a previously unknown fault zone, which absorbs only a minor portion of relative plate motion between the Pacific and Australia plates there. We attempt to obtain detailed information about fault geometry and rupture distribution of this event using InSAR data. Combining geological field survey observations with SAR displacement fringes, correlation, and range and azimuth offsets, we identify four faults which slipped during co-seismic rupture, of which seven segments are distinguished with various strikes and dip angles. Our inversion results show that the slip is concentrated in the upper 10 km depth. Slips along the Greendale fault (including four segments) are predominantly dextral with a maximum up to 8.5 m. The fault coinciding with the earthquake hypocenter slipped reversely up to ~5.1 m. The third fault located west of the Greendale fault also reversely ruptured, with a peak of ~3.5 m. Slip on the fourth fault located north of the Greendale fault and east of the second fault is minor, no more than 1.9 m. We also compare the top 1 km slip along the Greendale fault with surface rupture distribution, and find very good agreement between the two. The maximum surface slip is about 6 m, located about 26 km east of the west end of the fault surface rupture. The total seismic moment release is 5.0×1019N·m, equivalent to an Mw=7.12 event. Main features of InSAR data are well recovered, the residuals near the epicenter are less than 20 cm, confirming good data fitting of our fault slip model. Based on this fault slip model we calculate about 1 bar of Coulomb stress change at the hypocenter of the 2011 Mw6.3 Christchurch earthquake, located about 30 km east of the Darfield earthquake.
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