Physical mechanism for severe seismic hazard in the 2010 Yushu, China, earthquake (Mw= 6.9): insights from FEM simulations

Abstract

The moderate-size 2010 Yushu earthquake (Mw 6.9) caused severe seismic damage around the source region which is situated on the sparsely populated hinterland of the Tibetan Plateau. But until now the mechanisms have not been well understood. To this end, we constructed the model to simulate the fault spontaneous rupture propagation, in which the realistic fault with a curved bend is imbedded. Our modeling results show that the special fault geometry controlled the rupture behavior, which encouraged rupture propagation speed transition from subshear to supershear with the speed of 5.17 km/s larger than the local shear wave velocity. Moreover, calculation results demonstrated that strong ground motion acceleration was greatly intensified by supershear ruptures, leading to widespread destruction. This may be the main reason why serious earthquake damage happened in the Yushu earthquake. In particular, we can see from numerous numerical experiments that rupture styles will be different if geometries of fault are varied. It is confirmed that it is the special geometry of the seismogenic fault of the Yushu mainshock produced grave seismic hazard. Thus, deeply investigating fault geometry will be helpful to better understand seismic source process and seismic hazard assessment.Key Points Curved bend in the seismogenic fault for the 2010 Yushu earthquake encouraged the supershear rupture transition. Strong ground motion acceleration was greatly intensified by supershear ruptures. Special geometry of the fault of the Yushu mainshock lead to seriouos seismic damage.