Pre-, Co-, and Post-Seismic Fault Slip in the Northern Chile Seismic Gap Associated with the April 1, 2014 (Mw 8.2) Pisagua Earthquake.

Wednesday, 17 December 2014: 5:15 PM
Mark Simons1, Zacharie Duputel2,3, Eric Jameson Fielding4, John Galetzka5, Joachim F Genrich1, Junle Jiang1, Romain Jolivet1, Hiroo Kanamori1, Angelyn W Moore4, Francisco H Ortega Culaciati6, Susan E Owen4, Bryan V Riel1, Luis A Rivera2, Daniel Carrizo7, Nathalie Cotte8, Jorge Jara8, Jürgen Klotz9, Edmundo O Norabuena10, Ismael Ortega11, Anne Socquet8, Sergey V Samsonov12 and MariaCarolina Valderas Bermejo11, (1)Seismological Laboratory, Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, United States, (2)Institut de Physique du Globe de Strasbourg, Strasbourg, France, (3)CNRS, Paris Cedex 16, France, (4)Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, United States, (5)UNAVCO, Inc. Boulder, Boulder, CO, United States, (6)University of Chile, Department of Geophysics, Santiago, Chile, (7)Universidad de Chile, Advanced Mining and Technology Center, Santiago, Chile, (8)ISTerre Institute of Earth Sciences, Saint Martin d'Hères, France, (9)Helmholtz Centre Potsdam GFZ German Research Centre for Geosciences, Potsdam, Germany, (10)Instituto Geofísico del Perú, Lima, Peru, (11)Universidad de Chile, Centro Sismologico National, Santiago, Chile, (12)Canada Center for Remote Sensing, Ottawa, ON, Canada
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.