摘要
2018年9月4日新疆伽师发生MS 5.5地震,震源区周边发生过数次的强震,且各震中位置相近,大致为10 km左右.由于地震观测报告给出的初始定位误差较大,余震分布较为离散,且震源区沉积层较厚,无断层出露,伽师地震的发震断层与前两次强震是否存在关联仍不清楚.本研究主要利用CAP方法对伽师地震MS≥3.5的余震震源机制解进行解算,并利用双差定位方法对伽师地震序列进行重定位.结果表明,伽师地震主震震源机制解为节面Ⅰ走向:226°,倾角90°,滑动角0°;节面Ⅱ走向:136°,倾角90°,滑动角-180°;本次地震为走滑型地震事件,主震震源深度为10 km,余震震源机制解与主震较为一致,P轴作用近似NS向,与区域构造应力场相同.根据双差定位结果显示,余震的优势分布方向为北东向,震源深度集中在5~15 km.由余震分布特征和震源机制解,认为此次地震断层面应为节面Ⅰ,与1997年和2003年的伽师强震属于不同的发震构造.根据相关地质及地震资料分析,推测此次地震发震断层为震源区下方的隐伏断裂,此断裂很可能即为与羊达曼断裂正交的北东向隐伏直立断层,伽师地震的发生与帕米尔、南天山以及塔里木盆地的相对形变速率和升降幅度有关.
On September 4,2018,the MS 5.5 earthquake occurred in Jiashi,Xinjiang.Several strong earthquakes occurred in this area,and epicenter was close to each other.Due to the large initial positioning error of the seismic observation report,the distribution of aftershocks is relatively discrete,and the sedimentary layer in the source area is thick,no fault is exposed.It is still unclear whether the seismogenic fault of the Jiashi earthquake is related to the previous two strong earthquake.In this study,the CAP method is used to solve the focal mechanism solution of the aftershock of the Jiashi earthquake with MS 3.5,and the double-different localization method is used to relocate the Jiashi earthquake sequence.The result show that the main Jiashi earthquake focal mechanism solution for nodal planeⅠdirection:226°,angle 90,sliding angle 0;nodal planeⅡdirection:136,angle 90,sliding angle-180;For the strike-slip earthquake event,the focal depth of the main shock is 10 km.the focal mechanism solution of the aftershock is consistent with the main shock,and the action of P axis approximates NS direction,which is the same as the regional tectonic stress field.According to the double-difference positioning results,the dominant distribution direction of aftershocks is northeast,and the focal depth is concentrated at 5~15 km.By the aftershock distribution and focal mechanism solution,think that the earthquake fault surface shall be the nodal planeⅠ,and with 1997 and 2003 Jiashi strong earthquake are different seismogenic structure.According to the relevant geological and seismic data analysis,it is speculated that the earthquake-induced fault is a hidden fault below the source region.This fault is likely to be the NE-trending erect fault perpendicular to the Yangdaman fault,and the occurrence of the Jiashi earthquake relative deformation rate and elevation of Pamir,South Tianshan and Tarim Basin.
作者
张志斌
金花
朱皓清
ZHANG Zhi-bin;JIN Hua;ZHU Hao-qing(Earthquake Administration of Xinjiang Uygur Autonomous Region,rümqi 830011,China)
出处
《地球物理学进展》
CSCD
北大核心
2019年第6期2232-2238,共7页
Progress in Geophysics
基金
地震监测、预报、科研、三结合课题( CEA-JC/3JH-173103)
测震青年骨干专项( CEA-JC/QNCZ-18313) 联合资助
关键词
伽师M_S
5.5地震
余震序列
双差定位
震源机制
隐伏断裂
Jiashi M_S 5.5 earthquake
Aftershock sequence
The double-difference algorithm
Focal mechanism
Buried faults
