宋超,
盖增喜^,
北京大学地球与空间科学学院地球物理系, 北京 100871

基金项目: 国家自然科学基金项目（41774047，41374045）资助


详细信息

作者简介: 宋超, 男, 1993年生, 硕士研究生, 主要从事震源机制反演和破裂过程成像研究.E-mail:chsong@pku.edu.cn

通讯作者: 盖增喜, 男, 1973年生, 副教授, 主要从事理论地震学和地震大地构造学方面的研究.E-mail:zge@pku.edu.cn

中图分类号: P315

收稿日期:2017-10-17
修回日期:2018-02-02
上线日期:2018-04-05

An iterative travel time inversion and waveform modeling method to determine the crust structure and the focal mechanism of 2015 Alxa Left Banner M_S5.8 Earthquake

SONG Chao,
GE ZengXi^,
Institute of Geophysics, School of Earth and Space Sciences, Peking University, Beijing 100871, China



More Information

Corresponding author: GE ZengXi,E-mail:zge@pku.edu.cn

MSC: P315

--> Received Date: 17 October 2017
Revised Date: 02 February 2018
Available Online: 05 April 2018


摘要
摘要:据中国地震台网测定，北京时间2015年4月15日15时39分，在内蒙古自治区阿拉善左旗（39.8°N，106.3°E）发生M_S5.8地震，震源深度为10 km.地震发生后多家机构对其开展了研究，本文使用喜马拉雅Ⅱ期布设在南北地震带北段的台站观测数据，通过走时反演和波形拟合反演的迭代，获得了该地区地壳一维速度结构，接着利用直达P波观测与理论走时差对震中位置重定位，然后反演地震的最佳双力偶解以及震源深度，最终得到了区域速度结构、地震的三维坐标、发震时刻以及震源机制解.结果显示，此次地震发生于世界时2015年4月15日7时39分26.718s，震中（39.7663°N，106.4304°E），震源矩心深度18 km，矩震级M_W5.25，节面Ⅰ走向176°，倾角85°，滑动角-180°，节面Ⅱ走向86°，倾角90°，滑动角-5°.结合该区域断裂带构造运动分析，本文认为此次地震是左旋走滑破裂，略带正断分量，断层面是节面Ⅱ，走向为NEE（近E-W）向，发震构造为震中附近的E-W向隐伏断裂.
关键词: 阿拉善地震/
相位加权叠加/
走时反演/
速度结构/
波形拟合/
震源机制

Abstract:According to CENC, an M_S5.8 earthquake occurred in Alxa Left Banner, Inner Mongolia Autonomous Region, China (39.8°N, 106.3°E) on 15:39, April 15, 2015(GMT+8), with a source depth of 10 km. After that, several researches were carried on this earthquake. Based on these previous results, we use observation data received by stations built on the northern part of Chinese North-South Seismic Belt during the Project Himalaya Ⅱ, to obtain a better regional 1-D crustal velocity structure successfully via an iterative travel time inversion and waveform modeling method. Then we relocate the epicenter with the travel time difference between Pg observation and synthesis, and re-inverse the best double-couple focal mechanism and depth. Finally, we determine the regional velocity model, 3-D location of hypocenter, origin time and focal mechanism. Our result shows that, the epicenter occurred at 07:39:26.718 on April 15, 2015 (UTC) is located at (39.7663°N, 106.4304°E) with the centroid depth of 18 km and of M_W5.25. The nodal plane Ⅰ has a strike of 176°, dip angle of 85° and slip angle of -180°, while plane Ⅱ has a strike of 86°, dip angle of 90° and slip angle of -5°. Considering the dynamic structure of local fault zone, we believe this earthquake is caused by a nearly pure left-lateral strike-slip fault with a few normal component. The nodal plane Ⅱ is the fault plane, which strikes towards NEE (nearly E-W). The seismogenic structure is likely to be an E-W striking buried fault near the epicenter.
Key words:Alxa earthquake/
Phase-weighted stack/
Travel time inversion/
Velocity structure/
Waveform misfit/
Focal mechanism



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