SEISMOLOGY AND GEOLOGY ›› 2021, Vol. 43 ›› Issue (2): 357-376.DOI: 10.3969/j.issn.0253-4967.2021.02.007

• Research paper • Previous Articles     Next Articles

PRELIMINARY STUDY FOR SEISMOGENIC STRUCTURE OF THE MS6.4 JIASHI EARTHQUAKE ON JANUARY 19, 2020

LI Jin1,2,3), JIANG Hai-kun4), WEI Yun-yun2), SUN Zhao-jie5)   

  1. 1)Xinjiang Pamir Intracontinental Subduction National Field Observation and Research Station, Urumqi 844000, China;
    2)Earthquake Agency of Xinjiang Uygur Autonomous Region, Urumqi 830011, China;
    3)Urumqi Institute of Central Asia Earthquake, China Earthquake Administration, Urumqi 830011, China;
    4)China Earthquake Networks Center, Beijing 100045, China;
    5)Kashi Standard Seismic Station of Earthquake Agency of Xinjiang Uygur Autonomous Region, Kashi 844000, China
  • Received:2020-09-04 Revised:2021-02-22 Online:2021-04-20 Published:2021-07-19

2020年1月19日伽师6.4级地震发震构造的初步研究

李金1,2,3), 蒋海昆4),*, 魏芸芸2), 孙昭杰5)   

  1. 1)新疆帕米尔陆内俯冲国家野外科学观测研究站, 乌鲁木齐 830011;
    2)新疆维吾尔自治区地震局, 乌鲁木齐 830011;
    3)中国地震局乌鲁木齐中亚地震研究所, 乌鲁木齐 830011;
    4)中国地震台网中心, 北京 100045;
    5)喀什基准台, 喀什 844000
  • 通讯作者: * 蒋海昆, 男, 1964年生, 研究员, 现主要从事余震序列及相关研究, E-mail: jianghaikun@sohu.com
  • 作者简介:李金, 男, 1986年生, 2012年于中国地震局地震预测研究所获固体地球物理专业硕士学位, 高级工程师, 主要从事数字地震学及地震预测研究工作, 电话: 15299475246, E-mail: lijin6205@163.com。
  • 基金资助:
    新疆维吾尔自治区自然科学基金(2020D01A83)、 国家重点研发计划项目(2018YFC1503305, 2018YFC1503206)、 中国地震局地震科技星火计划项目(XH21042)和新疆地震局科技创新团队计划(XJDZCXTD2020-3)共同资助

Abstract: On January 19, 2020, an MS6.4 earthquake occurred in Jiashi county. This earthquake located in the intersection of the three tectonic systems of South Tianshan, Tarim Basin and West Kunlun-Pamir. From 1997~2003 a group of strong earthquake swarms with MS≥6.0 occurred in this area, which constitute an extremely rare Jiashi strong earthquake swarm in mainland China. Based on the digital waveforms of Xinjiang Seismic Network, the best double-couple focal mechanisms of the main shock, foreshock and some aftershocks with MS≥3.6 were determined by CAP method, the Jiashi MS6.4 earthquake sequence was relocated by multi-step locating method. We analyzed the characteristics of focal depth, focal mechanisms and source rupture to determine the seismogenic structure. The nodal plane parameters of the best double-couple focal mechanism by CAP method are: strike 190°, dip 32° and rake 31° for nodal plane Ⅰ, and strike 74°, dip 73° and rake 118° for nodal plane Ⅱ; the centroid depth is 12.1km. The focal mechanism of main shock is thrust type, but the MS5.4 foreshock is a strike-slip event with a focal depth of 17.1km, and the focal mechanism parameters are: strike 83°, dip 78°, rake 173° for nodal plane I and strike 174°, dip 83°, rake 12° for nodal plane Ⅱ. The foreshock and mainshock are very close in space, but the rupture types are quite different, which shows the complexity of the seismogenic structure. The relocated sequence shows two dominant distribution directions, namely, the near EW direction and the near SN direction. Most of the aftershocks in the sequence are distributed in the EW direction, parallel to the strike of the Kepingtage nappe structure. The MS5.4 foreshock and the MS6.4 mainshock are both located near the dominant distribution in the near NS direction, and have a certain spatial distance from the distribution of aftershocks in the near EW direction. This feature may reflect that the mainshock and subsequent aftershocks are located on different fault zones. Combined with the geological structural background near the source area, it is inferred that the seismogenic structure of the MS5.4 foreshock is a strike-slip fault L0 with a high dip angle in NNW direction, and the basic information of the seismogenic fault L0 may be: strike NNW(about 175°), the fault plane is nearly upright, and the fault depth can reach about 15km. L0 may be a branch fault of the NNW-directed seismogenic structural system of the Jiashi earthquake swarm from 1997 to 1998. Since most of the aftershocks distributed on the east side of the Fault L0, we judge that L0 and related faults may have a certain control effect on the distribution of aftershocks. According to the location of the main shock, the spatial distribution of aftershocks and the occurrence characteristics of the fault in the source area, it is inferred that the seismogenic structure of the Jiashi MS6.4 mainshock is a NS-directed gentle-dipping fracture. The main shock caused the simultaneous activity of the Kepingtage nappe structure, resulting in a dense distribution of aftershocks with a certain distance from itself.

Key words: Jiashi MS6.4 earthquake, focal location, focal mechanism solution, multi-step locating method

摘要: 文中基于新疆区域数字地震台网观测资料, 采用CAP方法反演了2020年1月19日伽师MS6.4主震、 前震和部分MS≥3.6余震的震源机制解和震源深度, 利用多阶段定位方法对本次伽师6.4级地震序列进行了重新定位, 并在此基础上分析了伽师6.4级地震序列的震源深度、 震源机制和震源破裂面特征, 探讨可能的发震构造。 初步结果显示, 利用CAP方法得到6.4级地震的最佳双力偶机制解为: 节面Ⅰ, 走向190°, 倾角32°, 滑动角31°; 节面Ⅱ, 走向74°, 倾角73°, 滑动角118°, 震源深度为12.1km, 表明其为一次逆冲型地震事件。 而5.4级前震为一次走滑型地震事件, 震源深度为17.1km, 震源机制解为: 节面Ⅰ, 走向83°, 倾角78°, 滑动角173°; 节面Ⅱ, 走向174°, 倾角83°, 滑动角12°。 根据重新定位结果, 结合震源区附近构造地质背景推断, 5.4级前震的发震构造为NNW向高倾角走滑断裂L0, 其可能为1997—1998年伽师震群NNW向发震构造体系的分支断裂。 由于绝大多数余震分布在L0断裂东侧, 判断L0及相关断层对余震分布可能具有一定的控制作用。 根据主震的位置和余震的空间分布特征及震源区断裂的产状特征推测, 伽师6.4级主震的发震构造为SN向的缓倾角破裂, 其滑动可能主要集中在柯坪塔格推覆构造滑脱面附近的区域, 但伽师6.4级地震可能引起了柯坪塔格推覆构造多条断裂同时活动。

关键词: 伽师6.4级地震, 震源位置, 震源机制解, 多阶段定位方法

CLC Number: