Fault rupture model of the 2008 Dangxiong (Tibet, China) Mw 6.3 earthquake from Envisat and ALOS data

Abstract

On October 6, 2008, an Mw 6.3 earthquake occurred in Dangxiong county, southern Tibetan Plateau. In this study, Synthetic Aperture Radar (SAR) images from Envisat ASAR C-band descending Track 176 and ALOS PALSAR L-band ascending Track 500 are processed to generate the coseismic deformation caused by the earthquake. To estimate the source model, a downhill simplex non-linear inversion method is used to determine the fault rupture geometry, and an automatic fault discretization technique is employed to divide the fault plane to construct the optimal slip model, in which the uncertainties of the fault parameters are assessed by a Monte Carlo method. The inversion results show that the earthquake strikes almost south–north and has a normal faulting focal mechanism with rake angle and slip of −111.7° and 1.33m, respectively. Peak slip of 2.15m is located at a depth of 7.5km. The estimated geodetic moment is 4.06×1018N m (Mw 6.37), 71.2% of which is released in the depth range 4.5–11km. The slip model suggests that coseismic slip also takes place at some fault patches near the earth’s surface and postseismic afterslip occurs below the coseismic rupture area after the earthquake.