Coseismic Slip Distribution of the 2001 Kokoxili, Northern Tibet, Earthquake, Constrained by GPS and Geological Field Survey Data

We analyze GPS data observed before and after the 2001 Mw 7.8 Kokoxili earthquake in northern Tibet to derive the coseismic deformation field of that earthquake. Using this coseismic displacement data set and geologically mapped surface break measurements, we invert for the coseismic slip distribution along the seismogenic East Kunlun fault. Our result shows that the earthquake on average ruptured from surface down to a depth of ~16.5 km (13.1~18.7 km at 70% confidence). The average slip is ~2.6 m left-lateral, with the maximum slip of ~5 m along the Kusai Lake segment of the fault. There is 2~3 m left-slip detected in a gap of measured surface rupture between the westernmost Sun Lake segment and the west end of the main rupture on the East Kunlun fault. We also determine 1.5~2.0 m left-slip along a segment beyond the east end of geologically mapped surface rupture. Vertical slip is insignificant (<< 1 m) along most part of the fault, it nevertheless shows a pattern of south side up west of and north side up east of 93E longitude respectively. The seismic moment release is estimated ~6.0×10 N.m, in good agreement with the seismological estimates.