Simulation of Dynamic Rupture Process and Near-Field Strong Ground Motion for the Wenchuan Earthquake

Abstract

ABSTRACT The 2008 Wenchuan earthquake that occurred in the Longmenshan thrust zone is the most serious natural disaster recorded in China’s densely populated areas over the past few decades. Its northeast-trending principal fault—the Yingxiu–Beichuan fault (YXBCF), has a complex, segmentary-cascaded geometry and was dominated by the thrust slip in the southwest section, while the right-lateral slip in the northeast section. Some previous works believe that there may have occurred a supershear rupture in the strike-slip-dominated northeast section. Here we revisited this earthquake by exploring the dynamic rupture mechanism of the principal fault and showed a hypothetical scenario with supershear rupture occurring in its northeast section. We utilized a 3D curve grid finite-difference method to simulate the spontaneous rupture process of the YXBCF and corresponding near-field strong ground motion. An appropriate focal process is obtained using the trial-and-error method within reasonable parameters, and its related responses are validated by geological investigations and geophysical inversions. Besides, a large hypothetical oblique propagating supershear rupture is shown between Beichuan and Nanba in the northeast section of the YXBCF. Its transition mechanism is related to the Gaochuan–Beichuan conjugated fault from the fault geometry perspective, and belongs to the joint action of fault barrier and free surface. Such a supershear scenario is not rejected by observations and could increase the credibility of the occurrence of supershear rupture in the northeast section of the YXBCF during the Wenchuan earthquake.