Yagi Yuji, Okuwaki Ryo, Enescu Bogdan, Lu Junjie
Faculty of Life and Environmental Sciences, University of Tsukuba, Tennodai 1-1-1, Tsukuba, Ibaraki, 305-8572, Japan.
Mountain Science Center, University of Tsukuba, Tennodai 1-1-1, Tsukuba, Ibaraki, 305-8572, Japan.
Sci Rep. 2023 Jan 20;13(1):1107. doi: 10.1038/s41598-023-27384-y.
In September 2022, two destructive earthquakes of moment magnitude (M) 6.6 (foreshock) and 7.1 (mainshock) occurred in Taitung County, south-eastern Taiwan. To understand their complex rupture processes, we analysed these earthquakes using the Potency Density Tensor Inversion method, which can stably estimate the rupture propagation process, including fault geometry, without overfitting the data. The analyses revealed that the major rupture of the foreshock propagated towards shallow depth, in a south-southwest direction, following an initial rupture that propagated towards the deeper part of the fault. The mainshock, with its epicentre on the north-northeast side of that of the foreshock, consists of two distinct episodes. During the first episode (0-10 s), the initial rupture propagated north-northeast, through a deep path, followed by the main rupture that propagated bilaterally in a north-northeast and south-southwest direction. The second rupture episode (10-16 s) started near the hypocentre of the mainshock, and the rupture propagated towards the shallow side of the fault. The results suggest that the stress concentration from both the foreshock and mainshock's first rupture episode may have caused the second rupture episode in the high fracture surface energy area between the foreshock and the first rupture episode of the mainshock. The irregular rupture process of the foreshock and mainshock may reflect the heterogeneity of stress and structure in the source region.
2022年9月，中国台湾东南部的台东县发生了两次破坏性地震，震级分别为6.6级（前震）和7.1级（主震）。为了解它们复杂的破裂过程，我们使用势能密度张量反演方法对这些地震进行了分析，该方法可以稳定地估计破裂传播过程，包括断层几何形状，而不会过度拟合数据。分析表明，前震的主要破裂在断层初始向深部传播之后，向浅部传播，方向为南偏西南。主震震中位于前震震中的北偏东北侧，由两个不同的阶段组成。在第一阶段（0 - 10秒），初始破裂沿深部路径向北偏东北方向传播，随后主破裂沿北偏东北和南偏西南方向双向传播。第二次破裂阶段（10 - 16秒）始于主震震源附近，破裂向断层浅部传播。结果表明，前震和主震第一次破裂阶段的应力集中可能导致了在前震和主震第一次破裂阶段之间的高断裂面能区域发生第二次破裂阶段。前震和主震不规则的破裂过程可能反映了震源区应力和结构的非均匀性。
