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Early Stage and Main Ruptures of the 2015 Mw8.3 Illapel, Chile, Megathrust Earthquake: Kinematic Elliptical Inversions and Dynamic Rupture Simulations
Journal of Geophysical Research: Solid Earth ( IF 3.9 ) Pub Date : 2021-04-19 , DOI: 10.1029/2020jb021207
Hideo Aochi 1, 2 , Sergio Ruiz 3
Affiliation  

We apply kinematic and dynamic modeling to the 2015 Mw8.3 Illapel, Chile, earthquake constrained by continuous high‐rate GPS and strong motion data. Kinematic inversion by elliptical patches allows us to rapidly outline the ruptured area with different time windows and frequency ranges. The preferred solution indicates that the main large patch in the north is preceded by a small one in the south close to the hypocenter with a time shift no greater than 20 s. The rupture directivity on the main patch suggests that the origin is at depth, away from the initial small hypocentral patch. We then construct dynamic rupture models to be consistent with the geometry obtained from the kinematic inversion. We estimate the fracture energy of the main patch to be ∼7.5 MJ/m2. The initial rupture of the small hypocentral patch does not trigger the main patch due to the gap in fracture energy, and thus another nucleation is set at depth. This can be regarded as a foreshock‐mainshock sequence rather than a direct cascade rupture growth. The ruptured area corresponds to the preexisting zone of large interseismic coupling prior to the Illapel earthquake. The historical seismicity of the previous century suggests a possible reconstruction of the asperity map, assuming that every earthquake represents a characteristic seismogenic patch. Therefore, the construction of dynamic ruptures with geodetic and seismological knowledge is possible and useful not only for reproducing known earthquakes but also for providing a physically constrained model for quantitative seismic hazard study.

中文翻译:

2015年Mw8.3智利伊拉佩尔特大地震的早期和主要破裂:运动椭圆反演和动态破裂模拟

我们将动态和动态建模应用于受连续高速率GPS和强运动数据约束的2015年智利伊拉佩尔Mw8.3地震。椭圆形斑块的运动学反演使我们能够快速绘制出具有不同时间窗口和频率范围的破裂区域。首选解决方案是,在北部的主要大斑块之前,在南部靠近震源的小斑块之前,其时移不大于20 s。主斑块上的破裂方向性表明其起源是在深度上,远离最初的小的次中心斑块。然后,我们构造动态破裂模型,使其与从运动学反演中获得的几何形状一致。我们估计主贴片的断裂能约为7.5 MJ / m 2。由于断裂能的间隙,小的下中央膜片的初始破裂不会触发主膜片,因此在深度处会形成另一个形核。这可以看作是前震主震序列,而不是直接的级联破裂增长。破裂区域对应于伊拉珀尔地震之前的大震间耦合的既存区域。假设每个地震都代表一个特征性的地震成因,那么上个世纪的历史地震活动表明可能会重建粗糙图。因此,利用大地测量和地震学知识构造动态破裂是可能的,不仅对再现已知的地震有用,而且对于为地震危险性定量研究提供物理约束模型也是有用的。
更新日期:2021-05-15
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