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Coseismic slip and afterslip of the 2015 Mw 8.3 Illapel (Chile) earthquake determined from continuous GPS data

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Mahesh N. Shrivastava (1) (2), Gabriel González (1) (2), Marcos Moreno (3), Mohamed Chlieh (4), Pablo Salazar (1) (2), C. D. Reddy (4), Juan Carlos Báez (5), Gonzalo Yáñez (1) (7), Juan González (1) (2), Juan Carlos de la Llera (1) (7).

Abstract

We analysed the coseismic and early postseismic deformation of the 2015, Mw 8.3 Illapel earthquake by inverting 13 cGPS time series. The seismic rupture concentrated in a shallow (<20 km depth) and 100 km long asperity, which slipped up to 8 m, releasing a seismic moment of 3.6 × 1021 Nm (Mw = 8.3). After 43-days, postseismic afterslip encompassed the coseismic rupture. Afterslip concentrated in two main patches of 0.50 m between 20 and 40 km depth along the northern and southern ends of the rupture, partially overlapping the coseismic slip. Afterslip and aftershocks confined to region of positive coulomb stress change, promoted by the coseismic slip. The early postseismic afterslip was accommodated ~53% aseismically and ~47% seismically by aftershocks. The Illapel earthquake rupture is confined by two low interseismic coupling zones, which coincide with two major features of the subducting Nazca Plate, the Challenger Fault Zone and Juan Fernandez Ridge.

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1) National Research Center for Integrated Natural Disaster Management, Chile. 
2) Universidad Católica del Norte, Antofagasta, Chile
3) GFZ Helmholtz Centre Potsdam, German Research Centre for Geosciences, Germany
4) Geoazur, Université de Nice Sophia-Antipolis, OCA, IRD, CNRS, Valbonne, France
5) Indian Institute of Geomagnetism, Navi Mumbai, India
6) Centro Sismológico Nacional, Universidad de Chile, Chile
7) Pontifica Universidad Católica de Chile, Chile