断层复杂性对地震余震衰减的影响－以2024年乌什M7.1地震为例

Influence of Fault Complexity on Aftershock Decay: A Case Study of the 2024 M7.1 Wushi EarthquakeYin Xinxin1,2 , Wang Shuwang1, Liang Xiaonan1, Ma Guanyu3

摘要:

地震余震活动及其衰减过程与区域构造环境密切相关。本文以2024年1月23日新疆乌什县M7.1级地震为例,基于精定位结果,采用断层网络重构(FNR)方法探究了该区域复杂的断层构造对余震序列特征的影响。研究发现,乌什地震主震区存在错综复杂的断层系统,除南北向主断层带外,还伴生多条次级断层分支,形成网状断裂结构。在主震区还残留一条近垂直的共轭断层面,暗示了多向断层滑移的可能性。余震沿主断层西南段呈线性展布,同时次级断裂带上也分布有大量散射态余震簇。这种复杂的几何形态和多向滑移行为,使得地震应力在各断层面间有效传递,导致余震活动持续发育。利用贝叶斯框架下的改进Omori模型,对余震序列进行参数反演。结果显示,该地震序列的p值高达1.57,K值为768.4,表征了其衰减极为缓慢、持续时间长、活跃度高的特点。

Abstract:

Aftershock activity and its decay process are closely related to the regional tectonic environment. In this study, we investigate the influence of complex fault structures on aftershock sequence characteristics, taking the M7.1 Wushi earthquake in Xinjiang, China on January 23, 2024 as an example. Based on the precisely relocated results, we employ the Fault Network Reconstruction (FNR) method to analyze the intricate fault system in the region. Our findings reveal that the mainshock area of the Wushi earthquake is characterized by an intricate network of fault systems, comprising not only the primary north-south trending fault zone but also numerous secondary fault branches, forming a mesh-like fracture structure. The presence of a near-vertical conjugate fault plane within the mainshock area, suggesting the possibility of multi-directional fault slippage. The aftershocks exhibit a linear distribution along the southwestern segment of the main fault zone, while scattered aftershock clusters are also observed along the secondary fault strands. This complex geometric configuration and multi-directional slip behavior facilitate effective stress transfer across various fault planes, leading to the sustained development of aftershock activity. Utilizing the modified Omori model within a Bayesian framework, we perform parameter inversion for the aftershock sequence. The results indicate that the earthquake sequence exhibits a high p-value of 1.57 and a K-value of 768.4, characteristic of an extremely slow decay rate, prolonged duration, and high aftershock productivity.