新疆伽师地区地壳三维速度结构及中强震震源机制揭示的区域孕震环境  

Regional Seismogenic Environment Revealed by the 3D Crustal Velocity Structure and Focal Mechanism of Moderate and Strong Earthquakes in Jiashi Area,Xinjiang,China

作　　者：梁姗姗 徐志国[3,4] 黄小宁[5] 张广伟 邹立晔 周元泽 Liang Shanshan;Xu Zhiguo;Huang Xiaoning;Zhang Guangwei;Zou Liye;Zhou Yuanze(College of Earth and Planetary Sciences,University of Chinese Academy of Sciences,Beijing 100049,China;China Earthquake Networks Center,Beijing 100045,China;National Marine Environmental Forecasting Center,Beijing 100081,China;Key Laboratory of Marine Hazards Forecasting,Ministry of Natural Resources,Beijing 100081,China;Kunlun Digital Technology Company Limited,Beijing 100007,China;National Institute of Natural Hazards,Ministry of Emergency Management of China,Beijing 100085,China)

机构地区：[1]中国科学院大学地球与行星科学学院,北京100049 [2]中国地震台网中心,北京100045 [3]国家海洋环境预报中心,北京100081 [4]自然资源部海洋灾害预报技术研究重点实验室,北京100081 [5]昆仑数智科技有限责任公司,北京100007 [6]应急管理部国家自然灾害防治研究院,北京100085

出　　处：《地球科学》2024年第2期451-468,共18页Earth Science

基　　金：地震科技星火计划项目(No.XH213703Y);中央高校基本科研业务费专项资金(No.E3E40401X2)。

摘　　要：为了详细探讨伽师震区上地壳精细速度结构与地震活动的关系,基于新疆数字地震台网提供的震相观测报告和宽频带波形数据,使用双差层析成像方法获得了伽师地区(76.5°E~78.0°E,39.3°N~40.3°N)2009年以来地震精定位结果和较高分辨率的三维V_(P)、V_(S)和V_(P)/V_(S)结构,并分析了2020年伽师M_(S)6.4地震序列中M_(S)≥5.0地震的全矩张量解,综合研究区域内地震时空分布特征、震源机制和速度结构等信息,探讨伽师震源区发震构造及孕震环境.结果表明,研究区重定位后的地震分布与已知断裂相关性差.2020年伽师M_(S)6.4地震序列呈NNW和近EW向2个优势方向分布,其余震在震后48 h内主要在距主震约20 km处近EW向的奥兹格尔他乌断裂上及其附近展布;序列中4次中强地震全矩张量解显示出具有明显的非双力偶成分,均为体积缩小的压性破裂;伽师地区地壳速度结构存在明显的不均匀性:2020年伽师M_(S)6.4地震震中位于P波高速体内、S波高速体边缘及低波速比区域,且在中下地壳存在大范围的S波低速异常.结合周边地质构造及前人研究结果,我们认为,2020年M_(S)6.4主震的发震构造为柯坪塔格推覆体中的近EW向隐伏逆断裂,与其共轭的NNW向隐伏断裂也参与了整个伽师M_(S)6.4地震序列的发震过程.伽师地区强震频发是塔里木盆地向南天山持续俯冲挤压,触发推覆构造和盆山交界处若干隐伏断裂活动的构造运动结果,速度结构所揭示的介质横向不均匀性也造成震源破裂机制的多样性.In order to discuss in detail the relationship between the fine velocity structure of the upper crust and seismic activity in the Jiashi area,this paper used the double-difference tomography method to obtain the earthquakes precise relocation results and highresolution three-dimensional V_(P) and V_(S) velocity structuresin the Jiashi region(76.5°E-78.0°E,39.3°N-40.3°N)with the seismic phase observation and broadband waveform provided by the Xinjiang Digital Seismic Network since 2009.The full moment tensor solutions of earthquakes with M_(S)≥5.0 in the 2020 M_(S)6.4 Jiashi earthquake sequence arecalculated,and the spatiotemporal distribution characteristics of earthquakes in this region are comprehensively studied.Theresults indicate that the earthquake distribution after relocation in this area has a poor correlation with distribution of the known faults.The 2020 M_(S)6.4 Jiashi earthquake sequence was distributed in two dominant striking direction:NNW and near EW.The aftershocks were mainly distributed on and near the Ozgertau fault with near EW-striking,about 20km away from the mainshock,within 48 hours after the earthquake.The full moment tensor solutions of the four moderately strong earthquakes in the sequence show significant non double-couple components,all of which are compressive fractures with reduced volume.The results show that there is obvious heterogeneity in the crustal velocity structure in the Jiashiarea.,the epicenter of the 2020 M_(S)6.4 Jiashi earthquake is located within high P-velocity zones,the margin of hightS-velocity zones and low VP/VS,zones,there are large-scale S-wave low velocity anomalies in the middle and lower crust.Integrated with the regional tectonics and previous research results,we believe that the seismogenic structure of the M_(S)6.4 mainshock in 2020 is the near EW buried nappe blind reverse fault in the Kepingtag nappe,and its conjugate NNW buried fault also participated in the seismogenic process of the entire M_(S)6.4 Jiashi earthquake sequence.The frequent occu

关 键 词：伽师地区 地震定位 速度结构 全矩张量 孕震环境 

分 类 号：P315[天文地球—地震学]