The Focal Mechanism and Stress Field Inversion in the Eastern Section of West Kunlun
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摘要: 本文利用新疆测震台网记录的宽频带波形数据，采用CAP方法反演西昆仑东段2010年1月—2018年12月MS≥3.0地震震源机制，并结合研究区早期的震源机制数据分区反演构造应力场。结果表明：研究区地震破裂类型以逆断型和走滑型为主，其次为正断型，过渡型最少；震源机制节面在NWW向存在明显优势分布且倾角较陡，压应力P轴在NNE向有优势分布且倾角较小，张应力T轴在NW-SE向有优势分布且倾角较小，说明研究区总体上主要以NNE向的水平挤压和NW-SE向水平拉张作用为主；西南区域应力结构为走滑型，东北区域应力结构为逆断型，最大主应力轴σ1方位的最优解都呈NNE向，但西南区域更偏东，东北区域水平作用更明显。东北区域的应力形因子R值较小，体现该区域的物质隆升相对于西南区域物质隆升分量大。Abstract: In this paper, based on the broadband waveform data recorded by Xinjiang Seismic Network, the focal mechanism of MS≥3.0 earthquake from January 2010 to December 2018 are inverted by CAP method in the eastern section of West Kunlun. Combined with the focal mechanism data in the early stage, the stress field in the study area is inversed. The results show that the seismic rupture types are mainly thrust type and strike-slip type, followed by normal fault type, and the transition type is the least in the study area. Nodal plane of focal mechanism is near NWW, the inclination angle is steep. P axis is near NNE, and the inclination angle is small.T axis is near NW-SE, the inclination angle is small. It indicates that the stress field of study area is mainly under action of NNE horizontal compression and the NW-SE horizontal tensional; The inversion results show that the stress structure in the southwest and northeast regions is quite different, the stress structure in the southwest region is strike-slip type, the stress structure in the northeast region is thrust type. The optimum solution of the maximum principal stress σ1 are NNE direction in southwest region and northeast region, but the southwest region is more east, and the horizontal effect in the northeast region is more obvious. The stress shape ratio R indicates that the material uplift in the southwest region is smaller than that in the northeast region.
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Key words:
- West Kunlun /
- Focal mechanism /
- Stress field /
- CAP /
- MSATSI
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图 1 研究区主要断裂和1976年以来强震震源机制
注：①和田隐伏断裂 ②铁克里克断裂 ③柯岗断裂 ④康西瓦断裂 ⑤喀喇昆仑断裂
Figure 1. The focal mechanism of strong earthquakes since 1976 and main faults in study area
图 2 研究区MS≥3.0地震震源机制三角分类
Figure 2. The triangle classification of focal mechanism with MS≥30 in study area
图 3 研究区MS≥3.0地震震源机制类型空间分布
Figure 3. Spatial distribution of focal mechanism with MS≥30 in study area
图 4 研究区震源机制参数归一化统计
Figure 4. The normalized frequency statistics of focal mechanism parameter in study area
图 5 构造应力场分区反演结果的球面投影图（彩色点表示95%的置信区间）
Figure 5. Result of stress field inversion(The 95% confidence intervals are plotted in color dots)
表 1 构造应力场分区反演结果
Table 1. Result of stress field inversion
分区 ${\sigma _1}$ ${\sigma _2}$ ${\sigma _3}$ 应力形因子R 方位/° 倾角/° 方位/° 倾角/° 方位/° 倾角/° 东北 14
（-76—94）14
（-7—36）106
（16—194）10
（-38—77）－129
（-308—-48）73
（3—89）0.41
（0.06—0.98）西南 29
（-1—93）26
（-8—64）169
（79—299）57
（-18—83）－70
（-214—-8）18
（-71—75）0.62
（0.13—0.99）注：以上的数值范围为各参数在95%置信度下的不确定性范围。 
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