西藏米林Ms6.9级地震余震定位和地壳浅层速度结构  

Aftershocks localization and shallow crustal velocity structure following the Ms6.9 Mainling earthquake in Tibet, China

作　　者：叶进 赵俊猛[1] 刘红兵[1] 张衡[1] 徐强[1] 陈树泽 Jin Ye;Junmeng Zhao;Hongbing Liu;Heng Zhang;Qiang Xu;Shuze Chen(Laboratory of Continental Collision and Plateau Uplift,Institute of Tibetan Plateau Research,Chinese Academy of Sciences,Beijing 100101,China;University of Chinese Academy o f Sciences,Beijng 100049,China)

机构地区：[1]中国科学院青藏高原研究所,中国科学院大陆碰撞与高原隆升实验室,北京100101 [2]中国科学院大学,北京100049

出　　处：《科学通报》2020年第15期1496-1505,共10页Chinese Science Bulletin

基　　金：国家重点研发计划(2016YFC0600301);国家自然科学基金(41776201,41974109);中国科学院A类战略性先导科技专项(XDA20070302);中国科学院设备研制项目(YJKYYQ20190075);中国科学院青年创新促进会(2018097)资助。

摘　　要：北京时间2017年11月18日06时34分,西藏自治区林芝市米林县发生了Ms6.9级地震.为监测余震活动,震后围绕震中架设了28套宽频带地震台站获取了180 d观测数据.利用hypoDD双差地震定位法和LOTOS-12算法对余震事件进行精定位.结果表明,余震以主震为中心NW-SE向展布长约50 km、宽约30 km,根据余震分布推测存在3条与西兴拉断裂走向基本一致的,倾角自西北端向东南端逐渐变陡的活动断裂.结合LOTOS-12算法同时获得地壳浅层约20 km深度以上的P波和S波速度扰动分布结果.主震处于波速高低异常转换带,余震主要发生在地震波P波和S波速度负异常区,反映震源区地层破碎、断裂分布集中的特点.整体上,以南迦巴瓦峰为界, P波和S波大致呈北部高速异常,南部低速异常特点.该现象可能与北侧拉萨地体相对完整且岩性古老刚冷,而南侧及南迦巴瓦变质体相对破碎且岩石生成年代较新岩性软热有关.此外,紧邻南迦巴瓦峰西北侧区域的体波高速异常现象可能与该区域石榴子石矿物富集有关.At 06:34 CST on November 18, 2017, an Ms6.9 earthquake struck Mainling prefecture, Nyingchi City, Tibet. The earthquake occurred at the frontier zone of collision and subduction in the eastern Himalayan syntaxis, a region of persistently strong compression between India and Eurasia. To monitor aftershock activity, the Institute of Tibetan Plateau Research, Chinese Academy of Sciences, installed 28 broadband seismic stations around the epicentral area and obtained180 days of seismic observation data. The average spacing between stations was approximately 5 km, which yielded good coverage of the source area and enriched the seismic data for the Eastern Himalayan syntaxis. In this paper, the hypodense events are refined by the hypo DD double-difference seismic location method and the local tomography software(LOTOS-12), an algorithm for seismic location and velocity structure imaging joint inversion. The hypo DD seismic localization method uses waveform cross-correlation technology to achieve positioning using the minimum residuals of the actual and theoretical travel times of two earthquakes. It is widely used for close-range earthquakes and is suitable for regional earthquake research;the LOTOS algorithm is more appropriate for velocity structure inversion in regions with significant differences in physical properties. The results show that the aftershock zone is approximately 50 km long and 30 km wide and trends NW-SE. According to the aftershock distribution, three active faults are basically consistent with the strike of the Xixingla fault zone. These active fractures are similar in shape and have a NE dip direction, and the dip angles of the active faults gradually become steeper from NW to SE. Under the continuous NE thrusting action of the Namche Barwa syntaxis, the three secondary fractures have undergone bending deformation. This deformation is associated with the adjustment mode of the eastern Himalayan syntaxis where the Indian plate continues to push Eurasia northward. At the same time, combining these

关 键 词：米林地震 喜马拉雅东构造结 地震定位 发震构造 速度结构 

分 类 号：P315[天文地球—地震学]