山西北部M_L2.2级地震空段与中强地震关系研究

Research on Relationship Between M_L2.2 Seismic Gap in Northern Shanxi and Moderate Earthquakes

2014年7月5日以来山西北部M_L2.2级地震空段被2015年5月20日天镇M_L3.1级地震打破,随后在空段周边陆续发生三次震群事件,中小地震震源机制解结果显示空段受华北主应力场控制,空段震例回溯和震群活动显示未来晋冀蒙交界区域存在发生中强地震的危险。GPS基线显示晋冀蒙交界区域应力场受华北主应力场控制且NE向的右旋剪切和压性应变在持续增强。空段打破后中小地震差视应力值有上升-下降-恢复的应力积累过程。综合分析认为:晋冀蒙交界区应力场在增强,山西北部M_L2.2级地震空区打破,对未来该区域发生中强地震有指示意义。

ML2.2 seismic gap in northern Shanxi since July 5, 2014 is broken on May 20, 2015 Tianzhen ML3.1 earthquake. Three swarms occurred subsequently in seismic gap surrounding. Focal mechanism solution of middle and small earthquakes show that seismic gap is controlled mainly by stress field of north China, and earthquake cases and swarm activity show that the juncture area of Shanxi, Hebei and Inner Mongolia exist the occurrence risk of mid-strong earthquake in the future. GPS baseline indicate that the juncture area of Shanxi, Hebei and Inner Mongolia is controlled mainly by stress field of north China and NE-trending dextral shearing and compression strain increase. After the break, differential apparent stress values of moderate and small earthquakes there is the increased-decreased-recovery stress accumulation process. In summary, stress field strengthen in the juncture area of Shanxi, Hebei and Inner Mongolia, after ML2.2 seismic gap in northern Shanxi broken, suggesting a certain significance to moderate earthquake prediction in this area.