Earthquake Focal Mechanisms in Yunnan and their Inference on the Regional Stress Field
Earthquake Focal Mechanisms in Yunnan and their Inference on the Regional Stress Field
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DOI：
10.1785/0120120309
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发表时间：
2013-08
影响因子：
3
通讯作者：
Li Zhao;Yan Luo;Ting-yu Liu;Yifan Luo
中科院分区：
文献类型：
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作者：
Li Zhao;Yan Luo;Ting-yu Liu;Yifan Luo
利用区域永久台网的宽频带地震记录，通过对P波和S波三分量波形的拟合，确定了2008年1月至2011年3月云南地区174次3.4≤ Mw ≤6.0中小地震的震源机制解。结果表明，地震主要是走滑机制，偶尔有正常和很少的逆冲断层事件。大多数地震发生在16公里深度以上的上地壳。然后，我们使用本研究中获得的震源机制并通过全球质心矩张量（GCMT）目录和Xu等人（2010）中的解进行增强，通过阻尼线性反演获得应力场的区域分布。反演结果表明，整个地区主要是在走滑断层制度。最大主轴和最小主轴的取向均呈现顺时针旋转模式。最大压缩轴大致为南北向，从华南地块的西北-东南向逐渐变化到印支地块的东北-西南向。这种模式是一致的地面水平速度来自大地测量观测。腾冲火山带和鲜水河-小江断裂带巧家段存在局部正断层应力区。在线资料：地震目录表和描述应力反演测试的图表。
Using the broadband records from a regional permanent network, we determined the focal mechanisms of 174 small and moderate earthquakes (3.4≤ M w≤6.0) from January 2008 to March 2011 in Yunnan, China, by fitting the three‐component waveforms of P and S waves. Results show that the earthquakes predominantly have strike‐slip mechanisms, with occasional normal and very few thrust‐faulting events. Most earthquakes occur in the upper crust above 16 km depth. We then derive the regional distribution of the stress field through a damped linear inversion using the focal mechanisms obtained in this study and augmented by the solutions in the Global Centroid Moment Tensor (GCMT) catalog and in Xu et al. (2010). Inversion results suggest that the entire region is predominantly under a strike‐slip faulting regime. Orientations of both maximum and minimum principle axes exhibit a clockwise rotational pattern. The axes of maximum compression are oriented roughly north–south, with a gradual change across the region from trending northwest–southeast in the South China block to trending northeast–southwest in the Indo‐China block. This pattern is consistent with the surface horizontal velocity derived from geodetic observations. Localized normal faulting stress regions are observed in the Tengchong volcanic zone and in the Qiao‐Jia segment of the Xianshuihe–Xiaojiang fault zone. Online Material: Tables of earthquake catalogs and figures describing stress inversion tests.