Inversion for coseismic slip distribution of the 2010 M w 6.9 Yushu Earthquake from InSAR data using angular dislocations

We used interferometric SAR (InSAR) crustal deformation data sets to explore the fault slip involved in the 2010 April 14 (M w = 6.9) Yushu earthquake modelled using angular dislocations. A refined rupture trace of the Yushu fault was extracted from two InSAR coseismic interferograms and field investigation results. We present a new method to discretize the fault geometry using triangular dislocation elements (TDEs), which are able to maintain consistency with the fault geometry modelled using rectangular dislocation elements (RDEs) and to avoid dislocation gaps and overlaps. Comprehensive comparisons between RDE and TDE models indicate that the classic Laplacian operator, which has not been carefully explored in many published studies, minimizes the slip on the boundary RDEs of the fault. A modification is proposed for the development of reasonable RDE models. The inversion shows that there were two larger concentrated slip zones during the Yushu earthquake. The largest was southeast of the hypocentre, near Luorongda, with a maximum slip of ∼1.6 m at the surface. The smaller slip patch was in the middle of the fault at a depth of ∼6 km, near the hypocentre. To improve the computational efficiency, we re-derived the analytic expressions for the strains associated with angular dislocations in an elastic half-space. The Coulomb stress changes increase at the northwestern and southeastern ends of the fault, and the small number of aftershocks in the southeast indicates that the seismic risk may be elevated in this area.