| 2019年四川长宁MS6.0地震序列重定位和震源特征分析 |
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| 引用本文： | 徐志国,梁姗姗,盛书中,张广伟,邹立晔,周元泽.2019年四川长宁MS6.0地震序列重定位和震源特征分析[J].地震学报,2020,42(4):377-391. |
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| 作者姓名： | 徐志国 梁姗姗 盛书中 张广伟 邹立晔 周元泽 |
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| 作者单位： | 1.中国北京 100081 国家海洋环境预报中心 |
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| 基金项目： | 国家自然科学基金（41804053）和中国地震局地壳应力研究所基本科研业务专项（ZDJ2019－16）联合资助 |
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| 摘 要： | 采用双差定位方法对2019年1月1日至2019年10月20日期间四川区域台网记录到的地震进行重定位，得到7 030个重定位事件，并获得了四川长宁MS6.0地震序列较准确的空间分布，并据此计算了震后长宁震源区的平均b值，分析了地震序列的活动性；利用近震全波形拟合方法获得了主震及4次MS≥5.0地震的震源机制解和矩心深度，初步分析了本次地震序列的发震构造，获得如下主要结果:① 四川长宁余震序列呈NW?SE向分布，余震深度分布整体呈现出西深东浅的趋势，且西部地区地震的频度远远高于东部地区；② b值空间分布显示，震后长宁地区呈现出明显的挤压构造环境；③ 主震和4次震级较大余震的矩心深度均较浅，尽管均为逆冲型为主的地震事件，但破裂面走向有所差异；④ 推测主震及中强余震是长宁背斜地区既有断裂或者同震过程中所产生的新生断层长期受到外力挤压而错断所致。
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| 关 键 词： | 长宁地震 重定位 b值 震源机制 发震构造 |
| 收稿时间： | 2019-11-25 |
Relocation and source characteristics of the 2019 Changning MS6.0 earthquake sequence |
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| Abstract: | The double difference earthquake location algorithm is used to relocate the earthquakes occurred in Changning area of Sichuan Province, which recorded by Sichuan regional network from January 1, 2019 to October 20, 2019, 7030 relocation events were obtained, and showing the clearer spatial distribution of Changning MS6.0 earthquake sequence. The average b-value of Changning focal area is calculated with relocated aftershocks catalog, and the seismicity of the earthquake sequence is analyzed. The focal mechanism solutions and centriod depth of the Changning main shock and 4 aftershocks with MS≥5.0 have been inverted with the local full-waveform inversion method, and the seismotectonics of this earthquake sequence was analyzed preliminarily. The main conclusions are as follow: ① The Sichuan Changning aftershocks distribute in a NW?SE trending, and the aftershocks show a trending of deep in the West and shallow in the East, and the frequency of earthquakes in the western part is much higher than that in the eastern part; ② The spatial distribution of b-value shows obvious compression tectonic environment in the Changning area after the occurrence of the earthquake; ③ The main shock and 4 moderate aftershocks occurred at unusual shallow centroid depths, and their focal plane solutions suggest that earthquakes occurred on thrust faults with slightly different strike; ④ It is speculated that the MS6.0 main shock and moderate aftershocks occurred on the preexisting faults, which subjected from a long-term compression force and the earthquake happened when the stress beyond the elastic limit, or the aftershocks generated on the newly generated faults created by mainshock coseismic rupture in Changning anticline area. |
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