摘要
2020年西藏尼玛M_(w)6.3地震发生在羌塘块体中部、依布茶卡-日干配错断裂系内的半地堑盆地内,基于震源机制解确定的发震断层存在较大差异。文中采用InSAR技术和Sentinel-1卫星升、降轨SAR数据获取了同震形变场,基于弹性半空间位错模型反演确定了发震断层参数,基于非均匀位错模型获得了断层面上的精细滑动分布。结果表明:1)在升、降轨InSAR同震形变场中,尼玛地震引起一椭圆形沉降区(长约12km,宽约8km),最大LOS向沉降值分别为-0.298m、-0.238m。2)同震位错以正断倾滑为主,兼有少许走滑分量,滑动主要集中在3~12km深度,最大滑动量达1.1m,位于7km深处。3)发震断层为依布茶卡-日干配错断裂西侧的分支断层,走向约为30°,倾角约为68°,滑动角约为-73°。4)此次地震的破裂模式显示依布茶卡-日干配错走滑断裂存在张性应力积累,羌塘块体中部处于张性应力状态。
The Qinghai-Tibet Plateau has always been one of the areas with frequent strong earthquakes in China.On July 23,2020,an M_(w)6.3 earthquake occurred in Nima,Tibet in a half-graben basin of the Yibug Caka-Riganpei Co fault zone in the central Qiangtang block.After the earthquake,many institutions have calculated the focal mechanism solutions based on seismic waves.Although there are differences in the source location and the parameters of the seismic fault,they all show that it is a normal fault earthquake.This is inconsistent with the strike-slip character of the Yibug Caka-Riganpei Co Fault.In addition,this earthquake is another strong earthquake that occurred on Yibug Caka-Riganpei Co Fault after the Gaize M;6.9 event on January 9,2008.Therefore,by studying this earthquake,we can better determine the tectonic movement of the seismogenic fault,so it has great significance for understanding the seismogenic mechanism and risk of the central Qiangtang block.The average elevation in the central Qiangtang is more than 4800 m,the environment is harsh and it is difficult to carry out the field survey of the earthquake.At the same time,GNSS sites near the epicenter are extremely sparse.Therefore,the InSAR technology,which has been successfully applied to several earthquakes in Qinghai-Tibet Plateau,and the Sentinel-1 SAR data,which can be downloaded free of charge,are used to study this earthquake.Firstly,we obtain the coseismic deformation field based on GAMMA software and select SRTM data with 30 m resolution(http://gdex.cr.usgs.gov/gdex/)as the reference DEM.In order to improve the orbit error in interferogram,the precise orbit data provided by ESA(https://qc.sentinel1.eo.esa.int/aux;oeorb/)is used for correction.The adaptive filtering method with filtering function based on local fringe spectrum is used to filter the interferograms,and the filtering windows are set to 128×128 and 32×32,respectively.This iterative filtering window setting from large to small can greatly improve the coherence of the interferogram.Un
作者
邱江涛
季灵运
刘雷
刘传金
QIU Jiang-tao;JI Ling-yun;LIU lei;LIU Chuan-jin(The Second Monitoring and Application Center,China Earthquake Administration,Xi'an 710054,China;Institute of Geology,China Earthquake Administration,Beijing 100029,China)
出处
《地震地质》
EI
CSCD
北大核心
2021年第6期1586-1599,共14页
Seismology and Geology
基金
国家自然科学基金(41904007)
中国地震局震情跟踪定向工作任务(2020010206)共同资助。
