利用区域宽频带数据反演鲁甸MS6.5级地震震源破裂过程

Based on the finite fault inversion method, we investigated the rupture process of the 3 August 2014 Ludian M_S6.5 earthquake by regional broadband data provided by China Earthquake Administration. The inversion results indicate that the Ludian earthquake occurred on NNW oriented sinistral strike-slip fault, and most of the rupture slips concentrated in the upper left side of the hypocenter with the peak slip of about 0.7 m. The results show that the rupture slip of this earthquake initiated from 11 km and propagated quickly to the shallower depth, and probably could touch the ground surface with a rupture length of 10 km. The total seismic moment released by the whole fault is 1.97×10¹⁸ N·m, which is equivalent to magnitude of M_w6.1, and most energy released at the first 15 s. Comparing with ordinary earthquakes, four obvious characteristics can be observed from the Ludian earthquake: (1) The majority of the rupture slips concentrated in the shallow depth (less than 10 km) and the maximum slip occurred at the depth of 3 km, and the rupture could be close to the ground surface, thus the shaking of the ground is very strong. (2) The stress drop is very high. Based on our model, the magnitude of the associated static stress drop of the Ludian earthquake is ~ 2.8 MPa. (3) The fault rupture of the earthquake propagated with a higher velocity, and expands to the surface at a speed of more than 2.5 km·s^-1. (4) The mainshock may ruptured a conjugate fault system. These four characteristics might be the main reasons why this earthquake caused massive human casualties and property losses.