Coseismic fault slip of the 2008 M[sub w] 7.9 Wenchuan earthquake estimated from InSAR and GPS measurements

Abstract

We infer co-seismic fault slip during the 2008 M[sub w] 7.9 Wenchuan earthquake from interferometric synthetic aperture radar (InSAR) and GPS observations of ground deformation. We use ALOS/PALSAR data from ascending orbits on six tracks, and we do not use data that are strongly affected by ionospheric perturbations. We use a fault model composed of three planar fault segments of the Beichuan fault, and one planar segment representing the parallel Pengguan fault. Maximum thrust-slip is up to 6.7 m near the surface, and occurs in two locations, near Yingxiu in the south and Beichuan in the center of the rupture. Maximum strike-slip is over 4 m, and occurs near Pingtong and Nanba along the northern end of the rupture. We find that the ratio of coseismic thrust- to strike-slip on the Beichuan fault decreases from 1.5 to 0.7 from the SW to the NE.