山东省乳山地区余震分布与速度结构研究

利用山东乳山流动观测台网资料，采用双差精定位方法重新确定2014-05以来山东乳山M3.2地震余震序列的分布；在此基础上，利用双差层析成像方法反演该地区的三维速度结构模型。结果显示，乳山地区的余震序列整体呈现出圆形聚集特征，优势分布主要集中在3~8 km深度，乳山震群集中区的余震活动主要发生在破裂集中的区域，在5 km深度最为集中，说明乳山震群主要发生的区域为上地壳；研究区不同深度的P波速度变化明显。由于离已知的主断层有一定的距离，因此可以判断余震分布集中区可能是乳山断裂的分支或者是一条新的隐伏断裂。

Research on Velocity Structure and Aftershock Distribution of Shandong Rushan

Based on the array data of Rushan, using the double-difference accurate location method, this article clarifies the sequence distribution of aftershocks occurring in Rushan, Shandong Province, since May 2014. We then invert the three-dimensional velocity model with double-difference tomography method. The data reveals that the aftershocks in Rushan generally gather circularly with a predominance distribution of 3-8 km nearby; the aftershocks of Rushan earthquake swarms occur mainly in rupture-concentrated regions, with most at the depth of 5 km, which proves that Rushan earthquake swarms happened primarily at the upper crust. The P-wave velocity at different depths in the researched regions show dramatic changes. Because of the certain distance from the already-known main faults, it can be estimated that aftershock-concentrated regions are the branch fault of Rushan or a new buried fault here.