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- Title
Early Stage and Main Ruptures of the 2015 Mw8.3 Illapel, Chile, Megathrust Earthquake: Kinematic Elliptical Inversions and Dynamic Rupture Simulations.
- Authors
Aochi, Hideo; Ruiz, Sergio
- Abstract
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. Plain Language Summary: The 2015 Mw8.3 Illapel (Chile) earthquake is considered one of the mega‐earthquakes of this century. This study constructs a dynamic rupture model which is consistent with the kinematic inversion and frictional parameter estimates. Our results support that the Illapel earthquake consists of a main large patch preceded by a smaller one by dozens of seconds. The ruptured area is consistent with the interseismic coupling map and the seismicity. These elements suggest that the Illapel earthquake occurred in a comprehensive way, and the shown strategy of simulation is applicable to other earthquakes to improve our ability to construct a constrained mechanical model for quantitative seismic hazard assessment. Key Points: Rapid kinematic slip inversion identifies a main patch in the north preceded by a small one in the south, with a time delayDynamic rupture simulations constrained by kinematic inversion reconstruct the early and main rupture process of the 2015 Illapel earthquakeThe ruptured area and heterogeneous slip patches can be reconstructed from the interseismic coupling map and agree with recorded seismicity
- Subjects
CHILE; EARTHQUAKES; KINEMATICS; EARTHQUAKE hazard analysis; INDUCED seismicity; INVERSION (Geophysics)
- Publication
Journal of Geophysical Research. Solid Earth, 2021, Vol 126, Issue 5, p1
- ISSN
2169-9313
- Publication type
Article
- DOI
10.1029/2020JB021207