2016年9月23日四川理塘M4.9和M5.1地震发震构造分析

doi:10.3969/j.issn.0253-4967.2017.05.006

摘要/Abstract

摘要： 2016年9月23日，在四川西部理塘县相继发生M4.9和M5.1地震，震中位于青藏高原东缘川滇块体西北部金沙江断裂带与理塘断裂带所夹持的区域。文中基于四川区域地震台网提供的震相报告和波形资料，采用多阶段定位方法，对理塘M4.9和M5.1主震及余震序列进行了重新定位。同时，利用CAP波形反演方法，获得了这2个主震的震源机制解、震源矩心深度与矩震级。根据重定位后的余震空间分布形态、M4.9和M5.1主震的震源机制解，结合等震线形态及震中附近主要构造的展布，分析认为，近EW走向、倾向N的哈嘎拉断裂带为理塘M4.9和M5.1地震的发震构造，与该断裂带走向和倾向一致的节面Ⅰ为同震断层面，断面倾角44°。理塘M4.9和M5.1地震可能是在西侧羌塘块体物质持续E向挤入作用下、位于理塘-巴塘地区上地壳内的近EW向哈嘎拉断裂张性运动所致。

关键词: 理塘M4.9和M5.1地震, 重新定位, 震源机制, 发震构造

Abstract: On 23 September 2016, two earthquakes with magnitude of M4.9 and M5.1 occurred successively near Litang city in Sichuan Province, southwestern China. These two events are located between two large-scale fault zones, i.e., the Jinshajiang and Litang faults, in the northwest of the Sichuan-Yuannan active block, eastern Tibetan plateau. Based on the phase data and waveform data from the Sichuan regional seismic network, the M4.9 and M5.0 mainshocks and 390 aftershocks have been relocated using the multi-step locating method, and the focal mechanism solutions and centroid depths for the two mainshocks were calculated by the CAP waveform inversion method. From the spatial distribution of the relocated aftershocks and fault plane solutions of the two mainshocks, combining with the seismic intensity map and tectonic setting, we suggested that the two earthquakes were generated by the E-W trending northward dipping Hagala fault. The nodal plane consistent with the strike and dip of the Hagala fault is interpreted as the coseismic rupture plane with a dip angle of 44° for both the M4.9 and M5.1 earthquakes. And we inferred that the M4.9 and M5.1 earthquakes may be resulted from the nearly E-W striking Hagala normal faulting in the upper crust between the Litang and Batang regions due to the continuous eastward extrusion of the material of the Qiangtang block in the west.

Key words: M4.9 and M5.1 Litang earthquakes, relocation, focal mechanism, seismogenic structure

中图分类号:

P315.63

易桂喜, 龙锋, 梁明剑, 张致伟, 赵敏, 祁玉萍, 宫悦, 乔慧珍, 汪智, 王思维, 帅莉蓉. 2016年9月23日四川理塘M4.9和M5.1地震发震构造分析[J]. 地震地质, 2017, 39(5): 949-963.

YI Gui-xi, LONG Feng, LIANG Ming-jian, ZHANG Zhi-wei, ZHAO Min, QI Yu-ping, GONG Yue, QIAO Hui-zhen, WANG Zhi, WANG Si-wei, SHUAI Li-rong. SEISMOGENIC STRUCTURE OF THE M4.9 AND M5.1 LITANG EARTHQUAKES ON 23 SEPTEMBER 2016 IN SOUTHWESTERN CHINA[J]. SEISMOLOGY AND GEOLOGY, 2017, 39(5): 949-963.

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