Relocation of mainshock and aftershocks of the2011 Yingjiang MS5.8 earthquake in Yunnan

Based on the 3-D travel-time tables and 3-D velocity model of SichuanYunnan region, we relocated the Yingjiang MS5.8 earthquake occurred in Yunnan Province on March 10, 2011, by using the simplex algorithm. The relocated mainshock is 97.901deg;E, 24.677deg;N, and the focal depth is 13.1 km. Aftershocks were relocated by applying the double-difference method. The aftershocks show obviously spatial and temporal variation, and mainly distribute along the two sides of Dayingjiang fault and near the junction of the middle and northeast section of Dayingjiang fault. The length of the aftershock zone is about 12 km. Aftershocks were moving from southwest to northeast along the northeast segment of Dayingjiang fault, while near the junction between the middle and northeast segment of Dayingjiang fault aftershocks were moving to the middle segment of Dayingjiang fault gradually. The focal depths of aftershocks tend to migrate to the surface. The minimum depth of aftershocks in the first 10 hours approached to 2 km, indicating that the rupture is close to the surface. Combined with the relocation result, we analyzed the factors causing damage to buildings. The main reasons for the destruction of buildings include that the epicenter is located in the basin, the focal depth is shallow, and the epicenter distance is short to Yingjiang city.