• ISSN 2097-1893
  • CN 10-1855/P
陈平光,何骁慧,徐树峰,郑文俊,刘婷,刘智良. 2023. 喜马拉雅东构造结地震精定位及其区域应力场研究. 地球与行星物理论评(中英文),54(6):667-683. doi: 10.19975/j.dqyxx.2022-067
引用本文: 陈平光,何骁慧,徐树峰,郑文俊,刘婷,刘智良. 2023. 喜马拉雅东构造结地震精定位及其区域应力场研究. 地球与行星物理论评(中英文),54(6):667-683. doi: 10.19975/j.dqyxx.2022-067
Chen P G, He X H, Xu S F, Zheng W J, Liu T, Liu Z L. 2023. Earthquake relocation and regional stress field around the eastern Himalayan syntaxis. Reviews of Geophysics and Planetary Physics, 54(6): 667-683 (in Chinese). doi: 10.19975/j.dqyxx.2022-067
Citation: Chen P G, He X H, Xu S F, Zheng W J, Liu T, Liu Z L. 2023. Earthquake relocation and regional stress field around the eastern Himalayan syntaxis. Reviews of Geophysics and Planetary Physics, 54(6): 667-683 (in Chinese). doi: 10.19975/j.dqyxx.2022-067

喜马拉雅东构造结地震精定位及其区域应力场研究

Earthquake relocation and regional stress field around the eastern Himalayan syntaxis

  • 摘要: 喜马拉雅东构造结地处印欧大陆碰撞前缘,主要受喜马拉雅、拉萨、羌塘、川滇等地块和印度板块相互作用,区域构造变形强烈,是喜马拉雅造山带变形最强烈的地区之一,地震频发且主要呈条带状展布. 为揭示该地区地震活动及发震机制、断裂现今运动状态和区域应力应变模式,本文以喜马拉雅东构造结及周缘地区为研究区,采用双差定位法对2008—2018年间65663个M≥1.0的地震事件进行重定位,应用CAP方法对2009—2021年间163个M≥3.5的地震事件进行震源机制解反演. 在此基础上,收集研究区前人所得震源机制解共1156个,使用区域阻尼应力张量反演获得了中上地壳(0~35 km)区域应力场. 研究结果显示,区内地震主要沿断裂展布,其中喜马拉雅东构造结、高原中部拉张裂谷、川滇地块和滇缅地块地震活动频繁. 地震深度主要分布于5~25 km,川滇和滇缅地块内部地震相对于拉萨、羌塘地块的数量和优势深度有明显增大. 不同类型的震源机制分布具有明显规律性,东构造结处各种机制类型地震频发;走滑型震源机制主要沿大型边界断裂分布;正断机制地震发生于川滇地块的西边界断裂;逆断地震发育于印欧大陆碰撞前缘. 研究区主压应力轴水平方向从喜马拉雅、拉萨、羌塘、川滇、滇缅地块大致以东构造结为中心近顺时针旋转,且东构造结顶部、川滇地块北西部等地区呈现出强烈的局部不均匀性.

     

    Abstract: The eastern Himalayan syntaxis is located at the front of the collision between the Indian and Eurasian continents. This region is affected by the interaction of the Himalayan, Lhasa, Qiangtang, and Sichuan-Yunnan blocks and the Indian plate and is characterized by strong tectonic deformation with frequent earthquakes primarily distributed linearly. In this study, various seismological methods were used to reveal the seismicity, seismogenic mechanism, and tectonic stress field in this region. First, we used the double-difference location method (HypoDD) to relocate 65663 earthquakes with M ≥1.0 during 2008-2018. Then, the Cut-And-Paste (CAP) method was adopted to invert the focal mechanism solutions of 163 events with M ≥3.5 from 2009 to 2021. Combining the focal mechanisms inverted in this study and 1156 solutions collected from the GlobalCMT catalog and other published studies, we obtained the regional stress field with the damped regional-scale stress tensor inversion method. The results show that the earthquakes in this region are mainly distributed along mapped faults, among which the eastern Himalayan syntaxis, the extensional rift in the middle of the plateau, the Sichuan-Yunnan block, and the Yunnan-Burma block experience significant seismic activity. The earthquakes are distributed in the upper and middle crust (5-25 km), and there is a significant increase in the number and dominant depth distribution of earthquakes within the Sichuan-Yunnan and Yunnan-Myanmar blocks from those in the Lhasa and Qiangtang blocks. Earthquakes of various mechanisms occur frequently at the eastern Himalayan syntaxis; strike-slip earthquakes are mainly distributed along large boundary faults; normal earthquakes primarily occur along the western boundary faults of the Sichuan-Yunnan block, and thrust earthquakes are concentrated at the front of the collision between the Indian and Eurasian plates. The horizontal direction of the principal compressive stress axis rotates nearly clockwise around the eastern Himalayan syntaxis, from the Himalayas, Lhasa, Qiangtang, Sichuan-Yunnan to Yunnan-Burma blocks. Moreover, strong local inhomogeneity in the stress fields are found in the shallow eastern Himalayan syntaxis and northwest Sichuan-Yunnan block.

     

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