2015年1月山西介休M_L3.3震群发震原因初步研究

Causes for Jiexiu,Shanxi ML3.3 earthquake swarm in January 2015

2015年1月15~27日,山西介休发生M_L3.3震群活动。精定位结果显示：震源体很小,震源较浅;根据震源谱拐角频率和视应力特征认为,本次震群活动与水库诱发地震有相似之处。鉴于本次震群孕震过程可能有水等流体的参与,本文综合构造环境、震源参数、介休井水位升降以及不同时段区域应力场分析等,对介休震群发震原因进行了探讨。初步认为介休地区裂隙发育,地下水渗透、扩散使得地壳浅部岩体强度弱化,是山西介休M_L3.3震群发震的主要原因。同时,地下水渗透使得该区地震波高频成分衰减强烈,拐角频率和视应力明显低于山西其它地区同震级地震的水平。

From January 15 to January 27 in 2015,a M_L3.3 earthquake swarm happened in Jiexiu,Shanxi. The results of accurate location showed that seismic sources were small and the depth of hypocenter was shallow. In ferms of the characteristics of corner frequency and apparent stress,the activity of earthquake swarm was similar with reservoir induced earthquakes. Considering water＇s participation in seismic process,this paper discussed the causes for the Jiexiu earthquake swarm by the analysis of tectonic environment,seismic source parameters,fluctuation of Jiexiu well and the regional stress field in different periods. All the evidences showed that fracture,groundwater infiltration and diffusion which weakened rock mass＇ s strength were the main reasons for Jiexiu,Shanxi M_L3.3 earthquake swarm. At the same time,the seepage of groundwater made seismic wave attenuate sharply,and the corner frequency,as well as apparent stress,was lower than other area in Shanxi,which had same magnitude level.