Pre-, Co-, and Post-Seismic Fault Slip in the Northern Chile Seismic Gap Associated with the April 1, 2014 (Mw 8.2) Pisagua Earthquake.
Prof. Mark Simons, Ph.D.1, Zacharie Duputel2,3, Eric Jameson Fielding4, John Galetzka5, Joachim F Genrich6, Junle Jiang6, Romain Jolivet6, Hiroo Kanamori7, Angelyn W Moore8, Francisco H Ortega Culaciati9, Susan E Owen10, Bryan V Riel6, Luis A Rivera11, Daniel Carrizo12, Nathalie Cotte13, Jorge Jara14, Jürgen Klotz15, Edmundo O. Norabuena16, Ismael Ortega17, Anne Socquet18, Sergey V Samsonov19 and MariaCarolina Valderas Bermejo17, (1)California Institute of Technology, Seismological Laboratory, Pasadena, CA, United States, (2)Université de Strasbourg-CNRS, Institut de Physique du Globe de Strasbourg, UMR-7516, Strasbourg, France, (3)University of Strasbourg, Strasbourg, France, (4)Jet Propulsion Laboratory, California Institute of Technology, Pasadena, United States, (5)UNAVCO, Inc. Boulder, Boulder, United States, (6)Seismological Laboratory, Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, United States, (7)California Institute of Technology, Seismological Laboratory, Division of Geological and Planetary Sciences, Pasadena, CA, United States, (8)Jet Propulsion Laboratory/California Institute of Technology, Pasadena, United States, (9)University of Chile, Santiago, Chile, (10)Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, United States, (11)Institut de Physique du Globe de Strasbourg, Strasbourg, France, (12)Universidad de Chile, Advanced Mining and Technology Center, Department of Geology FCFM, Santiago, Chile, (13)ISTerre Institute of Earth Sciences, Saint Martin d'Hères, France, (14)Ecole Normale Supérieure, PSL Research University, CNRS UMR 8538, Laboratoire de Géologie, Laboratoire de Géologie, Paris, France, (15)Helmholtz Centre Potsdam GFZ German Research Centre for Geosciences, Potsdam, Germany, (16)Instituto Geofísico del Perú, Lima, Peru, (17)Universidad de Chile, Centro Sismologico National, Santiago, Chile, (18)University Grenoble Alpes, ISTerre, Grenoble, France, (19)Natural Resources Canada, Ottawa, ON, Canada
Abstract:
The April 1, 2014 (Mw 8.2) Pisagua Earthquake occurred in Northern Chile, within a long recognized seismic gap in the Central Andean region that last experienced major megathrust events in 1868 and 1877. We built a continuous GPS network starting in 2005, with the ultimate goal of understanding the kinematics and dynamics of this portion of the subduction zone. Using observations from this network, as well as others in the region, combined with InSAR, seismic and tsunami observations, we obtain estimates of inter-seismic, co-seismic and initial post-seismic fault slip using an internally consistent Bayesian unregularized approach. We evaluate the extent of spatial overlap between regions of fault slip during this different time periods. Of particular interest to this event is the extent and nature of any geodetic evidence for transient slow fault slip preceding the Pisagua Earthquake mainshock. To this end, we compare daily and high rate GPS solutions, the former of which shows long period transient motion started about 15 days before the mainshock and with maximum registered amplitude of 14.2 +/- 2 [mm] at site PSGA. Contrary to published findings, we find that pre-seismic deformation seen by the GPS network can be explained as coseismic motion associated with the multiple foreshocks.
