地震研究

利用云南数字地震台网的快报观测报告和地震事件波形数据,采用双差定位方法对2018年云南通海MS5.0地震序列进行重定位,使用Seis_CAP程序和改进的格点尝试法同时反演2次主震的震源机制解。重定位后,2次通海主震的震中位置分别为(24.188°N,102.726°E)和(24.191°N,102.725°E),震源深度分别为11.08 km和9.24 km。重定位结果显示,通海地震序列震中位置呈NE-SW向条带状分布,震源深度优势分布范围为3～12 km。震源机制解反演结果表明,2次主震均为走滑型地震,最佳拟合深度分别为8.1 km和6.4 km。综合分析重定位后地震序列空间分布、主震震源机制解和地质资料,认为小江断裂带中南段西支的明星—二街断裂或与其平行的隐伏断裂可能是此次地震的发震断裂。

Using catalog data and seismic waveform data recorded by the Yunnan Digital Seismic Network,we relocated Tonghai MS5.0 earthquake sequence with double-difference location algorithm.In the meantime,we inversed focal mechanism of the mainshocks with Seis_CAP program and improved grid point test method.After relocation,the epicentral location of Tonghai MS5.0 earthquake sequence exhibited in a narrow band along the NE-SW direction,and the predominant range of depth distribution was 3～12 km.The distance between two mainshocks was shorter after relocation,and the focal depth of two mainshocks were 11.08 km and 9.24 km respectively.The inversion results of focal mechanism show that the types of two MS5.0 mainshocks were both strike-slip earthquakes and the best fitting focal depts of them are 8.1 km and 6.4 km respectively.Based on the comprehensive analysis of the spatial distribution of Tonghai earthquake sequence after relocation,focal mechanism solutions and the geological data,we deduced that the seismogenic fault of Tonghai earthquake sequence may be the Mingxing-Erjie Fault or a hidden fault which was parallel to it in the western branch of the Xiaojiang Fault.

引言
1 数据选取和研究方法
2 通海地震序列重定位
3 震源机制解
4 讨论
5 结论

图1 通海MS5.0地震周边台站和断层分布<br/>Fig.1 The distribution of stations and faults near the epicenter of Tonghai MS5.0 earthquakes

图1 通海MS5.0地震周边台站和断层分布
Fig.1 The distribution of stations and faults near the epicenter of Tonghai MS5.0 earthquakes

图2 通海MS5.0地震序列原始定位震中分布图(a)和沿AA'(b)和BB'(c)深度剖面<br/>Fig.2 Initial epicenter distribution(a)and depth profiles along AA'(b)and BB'(c)of Tonghai MS5.0 earthquake sequence

图2 通海MS5.0地震序列原始定位震中分布图(a)和沿AA'(b)和BB'(c)深度剖面
Fig.2 Initial epicenter distribution(a)and depth profiles along AA'(b)and BB'(c)of Tonghai MS5.0 earthquake sequence

表1 通海震源区速度模型<br/>Tab.1 Velocity model of Tonghai earthquake area

表1 通海震源区速度模型
Tab.1 Velocity model of Tonghai earthquake area

图3 通海地震序列震相走时曲线<br/>Fig.3 Travel time curves of P and S phases of Tonghai MS5.0 earthquake sequence

图3 通海地震序列震相走时曲线
Fig.3 Travel time curves of P and S phases of Tonghai MS5.0 earthquake sequence

图4 通海地震序列震相—震中距统计图<br/>Fig.4 Phase-distance histogram of TonghaiMS5.0 earthquake sequence

图4 通海地震序列震相—震中距统计图
Fig.4 Phase-distance histogram of TonghaiMS5.0 earthquake sequence

图5 重定位后通海MS5.0地震序列的震中分布图(a)和沿AA'(b)和BB'(c)深度剖面<br/>Fig.5 Epicenter distribution(a)and depth profiles along AA'(b)and BB'(c)of relocated Tonghai MS5.0 earthquake sequence

图5 重定位后通海MS5.0地震序列的震中分布图(a)和沿AA'(b)和BB'(c)深度剖面
Fig.5 Epicenter distribution(a)and depth profiles along AA'(b)and BB'(c)of relocated Tonghai MS5.0 earthquake sequence

图6 8月14日MS5.0地震发生前通海地震序列震中分布图(a)和沿AA'(b)和BB'(c)深度剖面<br/>Fig.6 Epicenter distribution(a)and depth profiles along AA'(b)and BB'(c)of relocated Tonghai MS5.0 earthquake sequence before the MS5.0 earthquake on Aug.14,2018

图6 8月14日MS5.0地震发生前通海地震序列震中分布图(a)和沿AA'(b)和BB'(c)深度剖面
Fig.6 Epicenter distribution(a)and depth profiles along AA'(b)and BB'(c)of relocated Tonghai MS5.0 earthquake sequence before the MS5.0 earthquake on Aug.14,2018

图7 8月14日MS5.0地震发生后通海地震序列震中分布图(a)和沿AA'(b)和BB'(c)深度剖面<br/>Fig.7 Epicenter distribution(a)and depth profiles along AA'(b)and BB'(c)of relocated Tonghai MS5.0 earthquake sequence after the MS5.0 earthquake on Aug.14,2018

图7 8月14日MS5.0地震发生后通海地震序列震中分布图(a)和沿AA'(b)和BB'(c)深度剖面
Fig.7 Epicenter distribution(a)and depth profiles along AA'(b)and BB'(c)of relocated Tonghai MS5.0 earthquake sequence after the MS5.0 earthquake on Aug.14,2018

图8 2018年8月13(a),14日(b)2次通海主震矩张量反演波形拟合图<br/>Fig.8 Seismograms of moment tensor inversion of Tonghai mainshocks occurred on Aug.13(a)and Aug.14(b),2018

图8 2018年8月13(a),14日(b)2次通海主震矩张量反演波形拟合图
Fig.8 Seismograms of moment tensor inversion of Tonghai mainshocks occurred on Aug.13(a)and Aug.14(b),2018

图9 2018年8月13(a),14日(b)2次通海主震反演深度图<br/>Fig.9 Best focal depth of Tonghai mainshocks occurred on Aug.13(a)and Aug.14(b),2018

图9 2018年8月13(a),14日(b)2次通海主震反演深度图
Fig.9 Best focal depth of Tonghai mainshocks occurred on Aug.13(a)and Aug.14(b),2018

表2 Seis_CAP程序反演得到的2次通海主震震源机制解<br/>Tab.2 Focal mechanisms of Tonghai MS5.0 mainshocks inversed by Seis_CAP program

表2 Seis_CAP程序反演得到的2次通海主震震源机制解
Tab.2 Focal mechanisms of Tonghai MS5.0 mainshocks inversed by Seis_CAP program

表3 改进的格点尝试法求解得到的2次通海主震震源机制解<br/>Tab.3 Focal mechanisms of Tonghai MS5.0 mainshocks inversed by the improved grid point test method

表3 改进的格点尝试法求解得到的2次通海主震震源机制解
Tab.3 Focal mechanisms of Tonghai MS5.0 mainshocks inversed by the improved grid point test method

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备注

引言

1 数据选取和研究方法

2 通海地震序列重定位

3 震源机制解

4 讨论

5 结论

期刊信息