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。
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.
出处
《地震地质》
EI
CSCD
北大核心
2017年第5期949-963,共15页
Seismology and Geology
基金
国家自然科学基金(41574047)
四川赛思特科技有限责任公司西部大开发优惠政策节税资金投资项目(XDK2015001)
四川省外国专家局引智项目(S201637)
2017年地震监测预报跟踪专项共同资助
