门源地区应力场与发震断层研究

doi:10.12196/j.issn.1000-3274.2023.03.006

摘要/Abstract

摘要： 应力场和发震断层形态确定是地震动力学研究的重要基础。为采用震源机制确定2022年1月8日发生M_S6.9地震的青海省门源地区的应力场和断层形态, 本研究首先搜集1927年到2022年门源地区地震震源机制解资料, 对于同一地震具有多个震源机制解的情况, 将震源机制中心解作为该地震震源机制, 是求解应力场和断层形态的基础数据, 而后采用整理得到的震源机制节面数据进行聚类分析, 得到了该地震序列的可能断层面形状, 并求解了研究地区的构造应力场。最后将构造应力场投影到断裂面上, 估计断层面的滑动角, 并模拟了应力场与发震断层的关系。研究结果表明, 门源地震序列的总体断层走向、倾角分别为103.19°, 72.44°, 与野外地质调查的冷龙岭断裂的走向倾角具有一致性。门源地区的构造应力场压轴走向为242.37°, 倾伏角为0.93°, 张轴走向为334.79°, 倾伏角为68.98°, 可以解释为青藏块体东北缘向东北方向扩展的过程中受到稳定的阿拉善块体阻挡, 导致了该地区逆冲兼走滑的断层破裂体系。将应力场投影到门源地震序列的总体断层面上得到断层滑动角为50.68°, 相对剪应力和相对正应力值分别为0.822和-0.077, 说明门源地区在西藏地块和阿拉善地块的NE向挤压应力下, 在NWW—SEE向较陡的断裂上呈现较大的剪应力和较弱的挤压状态。

关键词: 2022年门源M_S6.9地震, 震源机制解, 应力场, 应力形因子, 聚类分析

Abstract: The determination of stress field and fault geometry is an important basis for earthquake dynamics. In order to determine the stress field and fault geometry in Mengyuan region, where occurred an M_S6.9 earthquake on Jan 8, 2022, by using focal mechanism, firstly, focal mechanisms were collected from 1927 to 2022 in Menyuan region of Qinghai Province. For multiple focal mechanisms of the same earthquake, the central focal mechanism solution was as the focal mechanism of the earthquake, and used as the basic data for solving the stress field and fault geometry. Then cluster analysis was carried out with the focal mechanism node data, to obtain the possible fault plane shape of the seismic sequence, and solve the tectonic stress field in the study area. Finally, the slip angle was estimated by projecting the tectonic stress field onto the fault plane, and the relationship between the stress field and the seismogenic fault was simulated. The results showed that the overall strike and dip angle of the Mengyuan earthquake sequence are 103.19° and 72.44°, respectively, which were consistent with the azimuth of the Lenglongling fault from field geological survey. The azimuth and plunge of the compressional, tensional axes of the tectonic stress field in the study region were 242.37°, 0.93°, 334.79°, and 68.98°, respectively. It could be explained that the NE spreading in northeastern margin of the Tibet block was blocked by the stable Alxa Block, resulting in a thrust and strike-slip fault system in the study region. By projecting the stress field onto the fault plane of the earthquake sequence, the slip angle of the fault was estimated as 50.68°, the relative shear stress and normal stress were 0.822 and -0.077, respectively, which indicated that the Menyuan area had a large shear stress and a weak compression state on the steeper NWW—SEE fault under the NE-trending compressive stress of the Tibet and Alxa Massifs.

Key words: 2022 Menyuan M_S6.9 earthquake, Focal mechanism solution, Stress field, Stress shape factor, Cluster analysis

中图分类号:

P315.7

杨成, 万永革. 门源地区应力场与发震断层研究[J]. 地震, 2023, 43(3): 77-90.

YANG Cheng, WAN Yong-ge. Study on Stress Field and Seismogenic Fault in Menyuan Area[J]. EARTHQUAKE, 2023, 43(3): 77-90.

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