摘要
2017年9月2日宁夏固原市原州区发生4.6级地震.通过对此次地震的回顾和总结,得到以下结论:①固原4.6级地震为孤立型地震;余震主要分布在主震震中西南侧,结合震源机制节面解,初步判定NW向节面应为此次地震的发震断层面,震源错动方式为左旋走滑兼具逆冲;震源机制解最佳拟合深度为9 km;震源机制解参数为节面Ⅰ:走向34°、倾角62°、滑动角174°,节面Ⅱ:走向127°、倾角85°、滑动角28°;②固原4.6级地震前存在前震活动、小震调制异常以及固原地震窗异常;③海原小山钻孔应变异常变化与固原4.6级地震有关,且与该测项预测指标已有的研究结果较吻合,但此次地震震级比预计震级偏大;④固原地震台地电阻率和地磁谐波振幅比异常期间发生了3次中强地震,其中,2017年5月17—20日,固原地震台地电阻率EW向出现快速下降,之后呈低值变化;固原地震台地磁谐波振幅比NS向从2014年开始经历下降—转折—回升过程,具有良好的映震效能.
On September 2,2017,an M 4.6 earthquake occurred in Yuanzhou District,Guyuan City,Ningxia Hui Autonomous Region.Based on the review and summary of the earthquake,the following conclusions can be drawn:①Guyuan M 4.6 earthquake is an isolated earthquake;aftershocks are mainly distributed in the southwest of the epicenter.Combined with the focal mechanism nodal plane solution,it is preliminarily determined that the NW-trending nodal plane should be the fault plane of this earthquake,and the source dislocation mode is both left-lateral strike-slip and reverse.Rush.The optimum fitting depth of focal mechanism solution is 9 km.The focal mechanism solution parameters are nodal I:strike 34°,dip 62°and slip 174°;nodal II:strike 127°,dip 85°and slip 28°.②Before the Guyuan M 4.6 earthquake,there were foreshock activities,small earthquake modulation anomaly and Guyuan earthquake window anomaly.③The variation of borehole strain anomaly in Xiaoshan,Haiyuan is related to Guyuan M 4.6 earthquake,and is in good agreement with the research results of prediction index of this item,but the magnitude of this earthquake is larger than the predicted magnitude.④Three moderate-strong earthquakes occurred during the period of abnormal development of Guyuan geo-resistivity and Guyuan geomagnetic harmonic amplitude ratio.From May 17 to 20,2017,the EW of Guyuan geo-resistivity declined rapidly and then changed to a low value.The curve of Guyuan geomagnetic harmonic amplitude ratio NS to different periods has experienced a decline-turn-rise since 2014.Cheng has good seismic reflection ef ficiency.
作者
李文君
曾宪伟
卫定军
李国斌
罗国富
LI Wenjun;ZENG Xianwei;WEI Dingjun;LI Guobin;LUO Guofu(Earthquake Agency of Ningxia Hui Autonomous Region,Yinchuan 750001,China)
出处
《地震地磁观测与研究》
2020年第1期40-47,共8页
Seismological and Geomagnetic Observation and Research
基金
中国地震局地震科技星火计划(项目编号:XH18053Y)
宁夏地震科研基金课题(项目编号:NX201903)。
关键词
固原地震
震源机制
小震调制比
固原地震窗
钻孔应变
Guyuan earthquake
focal mechanism
small earthquake modulation ratio
Guyuan seismic window
borehole strain
