[S-CG43] スラブ内地震とその発生メカニズム

[SCG43-11] Seismic Potential in the Atacama Seismic Gap (Chile) Inferred from Interseismic Deformation and Interplate Coupling: Dismissing a Rigid Andean Sliver

★Invited Papers

*Francisco H Ortega Culaciati¹、Vicente Yañez-Cuadra^1,2、Marcos Moreno²、Andres Tassara³、Nicole Krumm-Nualart⁴、Javier Ruiz¹、Andrei Maksymowicz¹、Marina Manea^5,6,7、Vlad Constantin Manea^5,6,8、Jianghui Geng⁹ (1.Department of Geophysics, University of Chile, Chile.、2.Department of Geophysics, University of Concepcion, Chile、3.Department of Earth Sciences, University of Concepcion, Chile、4.Computation and Biology Laboratory, Fundacion Ciencia y Vida, Santiago, Chile.、5.Computational Geodynamics Laboratory, Centro de Geociencias, Universidad Nacional Autónoma de México, Campus Juriquilla, 76230, Querétaro, Mexico.、6.Astronomical Institute of the Romanian Academy, 040557, Bucharest, Romania.、7.Department of Geomorphology-Pedology-Geomatics, Faculty of Geography, University of Bucharest, Nicolae Balcescu 1, Sector 1, 010041, Bucharest, Romania.、8.Research Institute of the University of Bucharest–iCUB, University of Bucharest, 050095, Bucharest, Romania.、9.GNSS Research Center, Wuhan University, China.)

キーワード：Subduction Zones, Inverse Modeling, EPIC Tikhonov, Atacama, Interseismic, Coupling

Geodetically constrained interseismic interplate coupling has been widely used to assess seismic potential in subduction zones. Modelling interseismic deformation is complex, as involves interplate coupling and often ignored continental internal deformation processes. Here, we present a novel methodology to jointly estimate interplate coupling along with upper plate rigid motion and surface strain, constrained by GNSS-derived crustal velocities. We use a least squares inversion with a spatially variable Equal a Posteriori Information Condition (EPIC) Tikhonov regularization, accounting for observational and elastic structure uncertainties. We apply this approach to the Atacama Seismic Gap (Chile), inferring three megathrust regions with high tsunamigenic earthquake potential. Particularly concerning are 1) the megathrust region shallower than the 1995 (Mw 8.0) Antofagasta earthquake rupture, where a downdip segmentation is inferred, and 2) the region extending between the cities of Taltal and Copiapo. Our findings show surface motion dominated by strain, with negligible rigid motion, dismissing a rigid Andean microplate model typically assumed during the last 20 years.