2016年11月25日新疆阿克陶6.7级地震序列震源机制特征分析

The Characteristics of the Focal Mechanisms of MS6.7 Earthquake Sequence on November 25,2016 in Aketao,Xinjiang

摘要:

本研究利用新疆区域数字地震台网的波形资料，采用CAP方法反演了2016年11月25日阿克陶6.7级地震的前震、主震及11次M_S ≥ 3.6余震序列的最佳双力偶震源机制解，得到阿克陶6.7级地震最佳双力偶机制解：节面Ⅰ走向20°/倾角69°/滑动角-10°；节面Ⅱ走向114°/倾角81°/滑动角-159°，表明此次阿克陶6.7级地震为一次走滑型地震事件，结合震源区的地震地质构造及余震序列空间分布等已有研究成果，判定节面Ⅱ代表了主震的发震断层面。主震最大主压力轴方位为339°，与震源区附近历史中强震P轴近NW向的优势方位基本一致。其4.8级前震的震源机制解为走滑型，与主震震源机制解具有较高的一致性。11次余震中有6次为走滑型地震，3次为逆断型地震，1次正断型地震，1次混合型地震，且多数地震具有近NW向的P轴方位。此次6.7级地震序列的震源深度分布于6~16km之间，而大部分地震为9~13km，与本文计算得到的主震的震源深度10km相差不大。此外，初步分析了兴都库什-帕米尔地区强震活动与此次阿克陶6.7级地震的关系。

Abstract:

Based on the broadband waveforms recorded by Xinjiang Digital Seismic Networks,we inversed the focal mechanism solutions of the Aketao M_S6.7 main shock,foreshock and M_S ≥ 3.6 aftershocks by using CAP method. The results shows that the focal mechanism of the M_S6.7 strong earthquake had the nodal plane Ⅰ with strike 20°/dip 69°/rake -10° and the nodal plane Ⅱ with strike 114°/dip 81°/rake -159°. Combining with the seismo-tectonic background of the seismic area,nodal plane Ⅱ was identified to be the seismogenic fault plane of the main shock. The direction of P-axis for the main shock is 339°,which is close to the NW,preferred direction of the P-axis of historical earthquakes in this area. The focal mechanism solution of M_S4.8 foreshock is in high consistency with main shock. About six aftershocks are strike-slip type earthquakes,three aftershocks are thrust type earthquakes,one aftershock is normal type earthquake,and one aftershock is hybrid type earthquake. The P-axis of most earthquakes in the sequence yields the NW direction. The focal depth of this M_S6.7 earthquake sequence distributed at 6~16km,and most of the earthquakes occurred within the depth range at 9~13km,which is close to the focal depth of 10km of mainshock we calculated. Finally,we conducted a preliminary analysis on the relationship between the strong earthquakes in Hindu Kush Pamir region and this Aketao 6.7 earthquake.