2018年云南通海M_S5.0地震序列重定位及发震构造讨论

Relocation of Tonghai M_S5.0 Earthquake Sequence in 2018 and Discussion of it's Seismogenic Fault

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 M S5.0 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 M S5.0 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 M S5.0 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.