2019年长宁MS6.0地震周边区域速度与P波各向异性成像研究

doi:10.12196/j.issn.1000-3274.2023.04.001

摘要/Abstract

摘要： 利用基于程函方程求解的地震走时层析成像方法对2019年长宁M_S6.0地震震中及其周边区域进行反演成像, 获得了该区域高分辨率三维P波、 S波速度结构以及P波方位角各向异性参数分布, 并对几个典型剖面的泊松比结构进行了分析。结果表明, 方位角各向异性对地震波P波走时具有显著的影响; 研究区域上地壳速度结构存在显著的非均匀性, 且一些相对低速异常与注水采盐、天然气水力压裂开采及废水回注等工业活动区域具有明显的对应关系, 显示人类的工业活动可能已经对上地壳的物质性质产生了影响。长宁地震的发生可能由注水采盐活动直接诱发, 而由工业活动所造成的速度异常结构对区域内地震的发生可能产生的影响是持续性的。区域内P波方位角各向异性可能受板块运动和主压应力影响, 而长宁地震序列震源区域浅层P波方位角各向异性以近EW向为主, 与该区域的主压应力方向基本一致。这些结果为认识四川盆地东南缘精细地壳结构、深部物质运动和动力学机制提供了新的资料。

关键词: 2019年长宁M_S6.0地震, 层析成像, 三维速度结构, P波方位角各向异性

Abstract: In this paper, the eikonal equation-based seismic tomography method was used to invert the velocity structure of the source and surrounding area of the Changning M_S6.0 earthquake in 2019. High-resolution 3-D P- and S-wave velocity as well as the P-wave azimuthal anisotropy models are obtained, and Poisson's ratio of several typical profiles is analyzed. The results show that the azimuthal anisotropy significantly affects the P-wave travel times, revealing strong crustal heterogeneities in the study area. Some low-velocity anomalies have good spatial correspondence with industrial activities fields, which may indicate the properties of upper crustal media have been affected by the shale gas hydraulic fracturing, fluid injection in salt minefields, and/or disposal of wastewater in natural gas fields. The Changning M_S6.0 earthquake may be directly induced by salt mining by water injection, and the velocity anomaly structure caused by industrial activities may have a sustained effect on the occurrence of earthquakes in the region. The P-wave azimuthal anisotropy in this region may be dominated by the plate motion and principal compressive stress. The anisotropy in the shallow depth of the Changning earthquake source region shows near EW direction, which is consistent with the direction of regional principal compressive stress. These results provide new insight into the fine crustal structure, deep material movement, and dynamic mechanism in the southeastern margin of the Sichuan Basin.

Key words: The 2019 M_S6.0 Changning earthquake, Seismic tomography, 3-D velocity models, P-wave azimuthal anisotropy

中图分类号:

P315.7

杨唯佳, 周艳杰, 姜恩元, 石玉涛, 马啸, 贺茜君, 黄雪源. 2019年长宁M_S6.0地震周边区域速度与P波各向异性成像研究[J]. 地震, 2023, 43(4): 1-20.

YANG Wei-jia, ZHOU Yan-jie, JIANG En-yuan, SHI Yu-tao, MA Xiao, HE Xi-jun, HUANG Xue-yuan. Tomographic Study on the Velocity Structures and P-wave Azimuthal Anisotropy of the 2019 Changning M_S6.0 Earthquake Surrounding Area[J]. EARTHQUAKE, 2023, 43(4): 1-20.

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