广东东源MS4.8地震序列震源位置及周边地区P波三维速度结构

利用震源位置和速度结构的联合反演， 得到2012年2月16日广东东源M_S4.8地震序列的震源位置及震源区速度结构模型， 并进一步采用双差定位法对该序列位置重新定位． 结果显示， 东源M_S4.8地震是一次自上而下、 自西向东的单侧破裂过程， 破裂面积约3 km×5 km． 震源区地壳结构复杂， 埋深712 km处为一个速度达6.2 km/s的高速体， 主震的起始破裂位置位于高速体的顶部速度梯度较大的区域， 破裂面穿越整个高速体， 余震止于高速体下方的低速区底部(埋深约16 km)． 东源县锡场镇下方的这种高、 低速相间的结构， 表明地壳层间相邻物质性状的差异利于应变能的积累和释放， 因此东源地区具备发生中强地震的构造条件． 

Location of the Dongyuan MS4.8 earthquake sequence of Guangdong and 3D P-wave velocity structure in and around source region

In this paper, we determined the location of Dongyuan M_S4.8 earthquake sequence on 16 February 2012 and velocity structure of the source region using a simultaneous inversion method. On this basis we relocated the earthquake sequence using the double-difference location algorithm. The results show that the Dongyuan M_S4.8 earthquake fits a unilateral fracture model, and ruptured down and westward, with a rupture area of 3 km×5 km. A high velocity zone (HVZ) is at the depth of 712 km, with the velocity 6.2 km/s. The source rupture started from the top of the HVZ, where the velocity shows a large gradient. The ruptured area cuts across HVZ. All aftershocks are not beyond the lower bound, at 16 km, of low velocity zone, which is located below the HVZ. Such a structure of high velocity alternating with low velocity is propitious for strain energy accumulation and release. So Dongyuan region has a crust structure favourable to moderate earthquake occurrence.