2022年青海门源MW6.6地震震源动力学破裂过程

Dynamic source rupture process of the 2022 MenyuanMW6.6 earthquake,Qinghai Province

  • 摘要: 2022年1月8日青海门源MW6.6地震在地表产生了较强的破坏,为研究门源地震产生强地表破裂及阻碍托莱山东段应力释放的构造背景,本文采用谱元法模拟了门源地震曲面分支断层在实际地形下的动力学破裂过程。结果显示,破裂自初始破裂点沿断层上倾方向同时发生双侧破裂;受震源区上方高速P波异常体的影响,断层产生非连续破裂。在破裂传播到托莱山东段时,断层的滑动速度和滑动量发生明显的阶跃式下降;此外,近地表处滑动速率约3.6 m/s的区域可能为强地面运动生成区。以上两者产生的高频辐射共同作用可能是此次门源地震同震地表形变较强的主要原因。由动力学模拟结果计算得到的应变空间分布显示,托莱山东段南西侧与冷龙岭西段北东侧的应变以拉张为主,而冷龙岭西段南西侧的应变以挤压为主,这与门源地震震源机制解结果、门源地震所处的青藏高原东北缘北东向主压转为南西向迁移所处的构造背景以及ENE和WSW的震源区应力场方向一致。托莱山断裂东段受分支断层破裂过程的强烈抑制作用,其累积应力未完全释放,残留震级约为MW5.1,在门源地震库仑应力的触发作用下,未来有进一步破裂的可能。

     

    Abstract: On January 8, 2022, a significant earthquake with a magnitude of 6.6 struck Menyuan, Qinghai, which resulted in substantial surface damage. To investigate the geological context behind the strong surface rupture generated by the Menyuan earthquake and its impact on the inhibition of stress release in the eastern section of the Tuolaishan fault, the spectral element method was employed in this study to simulate the dynamic rupture process of the branching fault on actual terrain. The dynamic rupture simulation revealed that the rupture was initiated bilaterally along an upward direction from the initial rupture point. Under the influence of a high-speed P-wave anomaly located above the source area, the rupture displayed a non-continuous pattern. With the progression of the rupture into the eastern section of Tuolaishan, a significantly abrupt decrease occurred in both slip rate and slip. Furthermore, the area with a slip rate of around 3.6 m/s near the surface of the Earth could be considered as a strong motion generation zone. The combined influence of these factors, along with their high-frequency radiation, might have played a pivotal role in the pronounced coseismic surface deformation during the MW6.6 earthquake in Menyuan. As calculated from the dynamic simulation results, the spatial distribution of strain suggested that the southwestern side of the eastern section of Tuolaishan and the northeastern side of the western section of Lenglongling experienced predominantly tensile stress, with corresponding areas subjected to compression. This observation aligns with the focal mechanism solution and the geological context of the northeastern margin of the Qinghai-Tibet Plateau, where the direction of principal compressive stress transitions from north-south to southwest-northeast. Furthermore, the dynamic rupture process in the eastern section of Tuolaishan was strongly inhibited by the rupture of the branching fault. This led to incomplete stress release and a residual seismic magnitude of approximately MW5.1. Under the trigger of Coulomb stress from the Menyuan earthquake, further rupture in the future is a possibility.

     

/

返回文章
返回