| 2017年四川九寨沟MS7.0强震的余震重定位及主震震源机制反演 |
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| 引用本文： | 梁姗姗,雷建设,徐志国,徐锡伟,邹立晔,刘敬光,陈宏峰.2017年四川九寨沟MS7.0强震的余震重定位及主震震源机制反演[J].地球物理学报,2018,61(5):2163-2175. |
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| 作者姓名： | 梁姗姗 雷建设 徐志国 徐锡伟 邹立晔 刘敬光 陈宏峰 |
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| 作者单位： | 1. 中国地震台网中心, 北京 100045;
2. 中国地震局地壳应力研究所(地壳动力学重点实验室), 北京 100085;
3. 国家海洋环境预报中心(国家海洋局海洋灾害预报技术研究重点实验室), 北京 100081 |
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| 基金项目： | 中国地震局地壳应力研究所基本科研业务专项（ZDJ2015-17），国家自然科学基金项目（41530212，41674091），科技部国家重点研发计划（2016YFC0600408），中国科学院战略性先导专项B类（XDB18000000）和郯庐断裂带专项（TYZ20160111）资助. |
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| 摘 要： | 本文采用双差定位法对2017年8月8日至10月31日期间四川九寨沟MS7.0主震及5200个余震序列进行相对定位，得到4036个重定位地震事件.采用中国区域地震台网观测到的宽频带垂直分向波形数据和W震相反演方法，得到了主震震源机制解.重定位结果显示，余震序列分别沿NNW和SSE两个方向扩展，展布长度约58 km，且这些余震主要集中在22 km深度之上.余震分布的另一个重要特点是具有分区特性，即在主震NNW方向约5 km处存在明显的西北和东南两区余震活动分界线；西北区的余震由深至浅具有较好连续性，而东南区却在约10 km深度处存在不连续性.余震分布的这种分区特征，说明九寨沟地震震源区的地壳结构存在强烈的不均匀性.余震分布与主震破裂特征的一致性，证实了我们定位结果的可靠性.主震的震源机制解展示出节面Ⅰ的走向/倾角/滑动角分别为246°/83.7°/-177°，而节面Ⅱ的走向/倾角/滑动角为155.7°/87.1°/-6.3°，最佳质心深度为15.5 km，矩震级MW为6.5.根据余震分布较为垂直和主震震源机制解两节面的倾角均在80°以上，并结合野外地质调查结果，推测此次九寨沟地震为与节面Ⅱ参数相近的一次高角度的左旋走滑型事件.
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| 关 键 词： | 九寨沟地震 余震序列 双差定位 W震相 震源机制 |
| 收稿时间： | 2017-09-25 |
Relocation of aftershocks of the 2017 Jiuzhaigou,Sichuan, MS7.0 earthquake and inversion for focal mechanism of the mainshock |
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| LIANG ShanShan,LEI JianShe,XU ZhiGuo,XU XiWei,ZOU LiYe,LIU JingGuang,CHEN HongFeng.Relocation of aftershocks of the 2017 Jiuzhaigou,Sichuan, MS7.0 earthquake and inversion for focal mechanism of the mainshock[J].Chinese Journal of Geophysics,2018,61(5):2163-2175. |
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| Authors: | LIANG ShanShan LEI JianShe XU ZhiGuo XU XiWei ZOU LiYe LIU JingGuang CHEN HongFeng |
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| Institution: | 1. China Earthquake Networks Center, Beijing 100045, China;
2. Key Laboratory of Crustal Dynamics, Institute of Crustal Dynamics, China Earthquake Administration, Beijing 100085, China;
3. Key Laboratory of Research on Marine Hazards Forecasting, National Marine Environmental Forecasting Center, State Oceanic Administration, Beijing 100081, China |
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| Abstract: | The Double-difference location method is used to determine the locations of the 8 August 2017 MS7.0 Jiuzhaigou main shock and its 5200 aftershocks till to 31 October, and finally the 4036 events are relocated. The W-phase method is applied to analyze the vertical-component data from China broadband regional seismic networks to determine the focal mechanism solutions of the main shock. Our relocation results show that the aftershocks extend toward NNW and SSE over about 58 km, most of which are located above 22 km depth. Another interesting feature of the aftershocks is block-like structures. There exists an obvious boundary 5 km north of the main shock, which separates the aftershocks in the northwest from those in the southeast. The NW aftershocks show a continuous feature from deep to shallow, whereas those in the SE have a discontinuous feature at about 10 km depth. Such a block-like structure suggests that there is a strong heterogeneity in the crustal structure around the Jiuzhaigou main shock. The distribution of aftershocks has a good match with the rupture displacement of the main shock, demonstrating the reliability of our relocated results. The focal mechanism solutions of the main shock show that the strike/dip/rake of the first nodal plane are 246°/83.7°/-177°, whereas those of the second nodal plane are 155.7°/87.1°/-6.3°. The optimal centroid depth of the main shock is 15.5 km, and its moment magnitude is 6.5. Using the nearly vertical aftershocks distribution and the two nodal planes with dips of larger than 80°, integrating with the field geological survey, we speculate that the Jiuzhaigou earthquake is,similar to the source parameters revealed in the second nodal plane, a left lateral strike-slip event with a large dip. |
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| Keywords: | 2017 Jiuzhaigou earthquake Aftershocks Double-difference location W-phase Focal mechanism solution |
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