摘要
2022年9月5日12时52分,川滇活动地块东边界的四川泸定地区发生6.8级强烈地震。在震中以北15km、以南25km的范围内开展震后现场考察,发现湾东村、幸福村、爱国村一带的磨西断裂沿线存在同震地表破裂迹象,而在震中以北、爱国村以南断裂通过的位置没有发育同震地表破裂。野外调查获得的同震地表破裂走向为320°~355°,运动性质为左旋走滑,位移量为20~30cm,运动性质和走向与震源机制解获得的结果一致。深入分析认为,本次四川泸定6.8级地震的同震地表破裂主要发育在泸定县磨西镇二台子以南—石棉县王岗坪乡爱国村之间,长度为15.5km。根据野外地质调查结果,并综合地震反演和形变观测已有结果等判定,四川泸定6.8级地震的发震构造为鲜水河断裂的南东段,即磨西断裂。结合余震分布时空演化特征分析进一步揭示,以磨西断裂二台子—新民乡段为主震破裂段的运动导致了此次6.8级地震的发生,并触发了震中以北的南门关—两河口段断裂的活动。泸定6.8级地震是一次主震破裂段发动、其后全段参与的较为复杂的事件。
The September 5,2022,M6.8 Luding earthquake occurred along the southeastern segment of the Xianshuihe fault zone.Tectonics around the epicenter area is complicated and several faults had been recognized.Focal mechanisms of the main shock and inversions from earthquake data suggest that the earthquake occurred on a northwest-trending,steeply dipping strike-slip fault,which is consistent with the strike and slip of the Xianshuihe fault zone.We conducted a field investigation along the fault sections on both sides of the epicenter immediately after the earthquake.NW-trending fractures that were recognized as surface ruptures during the earthquake,and heavy landslides along the fault section between Ertaizi-Aiguocun village were observed during the field investigations.There are no surface ruptures developed along the fault sections north of the epicenter and south of Aiguocun village.Thus it can be concluded that there is a 15.5km-long surface rupture zone developed along the Moxi Fault(the section between Ertaizi and Aiguo village).The surface rupture zone trends northwest and shows a leftlateral strike slip,which is consistent with the strike and motion constrained by the focal mechanism.The coseismic displacements were measured to 20~30cm.Field observations,focal fault plane,distribution of the aftershocks,GNSS,and In SAR observation data suggest that the seismogenic structure associated with the M6.8 Luding earthquake is the Moxi Fault that belongs to the southeastern segment of the Xianshuihe fault zone.Slip along the segment south of the epicenter generated this earthquake,and also triggered slip along a northeast-trending fault and the northwestern section of the Moxi Fault in the epicenter.So,the M6.8 Luding earthquake is an event that is nucleated on the section south of the epicenter and then triggered an activity of the whole fault segment.
作者
李传友
孙凯
马骏
李俊杰
梁明剑
房立华
LI Chuan-you;SUN Kai;MA Jun;LI Jun-jie;LIANG Ming-jian;FANG Li-hua(State Key Laboratory of Earthquake Dynamics,Institute of Geology,China Earthquake Administration,Beijing 100029,China;Sichuan Earthquake Agency,Chengdu 610041,China;Institute of Geophysics,China Earthquake Administration,Beijing 100081,China)
出处
《地震地质》
EI
CSCD
北大核心
2022年第6期1648-1666,共19页
Seismology and Geology
基金
第2次青藏高原综合科学考察研究(2019QZKK0901)
国家自然科学基金(42072250)共同资助。
关键词
泸定6.8级地震
地表破裂
发震构造
鲜水河断裂带
磨西断裂
the Luding M6.8 earthquake
coseismic surface rupture
seismogenic structure
the Xianshuihe fault zone
the Moxi Fault