福建仙游震群序列发震构造分析研究

Analysis of the Seismogenic Structure of the Xianyou Earthquake Swarm Sequence in Fujian Province

福建仙游地区自2010年8月开始出现地震序列活动,2012年地震活动水平有所提高,2013年以来地震活动水平进一步提高,ML3.0以上地震集中活跃。福建数字化地震台网对这些地震进行了较完整的监测,记录到丰富的观测资料。通过利用P、S波到时数据对ML≥1.0地震序列进行重新定位,发现地震序列空间位置和震源深度呈现出不同的时段性分布特征。同时利用福建数字化地震台网记录到的波形资料,采用"剪切-粘贴"法,获取了ML≥3.5的震源机制解和最佳震源深度。通过震群序列活动特征、震源位置分布、震源区断层活动分布以及震源机制解特征综合判断认为:仙游震群序列为库水下渗促使断裂滑动引起的构造地震,属于水库诱发型构造型地震,发震构造为穿过库区的NW向石苍断裂。

Earthquake swarm activities have been occurring in the Xianyou area of Fujian Province since August 2010.The level of seismic activity increased in 2012 and further increased in 2013,when M L≥3.0 earthquakes were concentrated.Sufficient observation data of these earthquakes were recorded by Fujian digital seismic network.In this study,the sequence of M L≥1.0 earthquakes are relocated using the P-and S-wave arrival data,and it is found that both the spatial location and focal depth of the earthquake sequence show different distribution characteristics for different periods.Meanwhile,based on the waveform data recorded by Fujian digital seismic network,the focal mechanism solutions and the best focal depths of M L≥3.5 earthquakes are obtained with the“cut and paste”method.According to the characteristics of earthquake swarm sequence,distribution of hypocenter location and fault activity in the hypocentral region,and the focal mechanism solution,it is concluded that the Xianyou earthquake swarm sequence are tectonic earthquakes caused by reservoir water infiltration and then fault slip,and thus,they are reservoir-induced tectonic earthquakes;in addition,the seismogenic structure is the NW-trending Shicang fault which passes through the reservoir area.