Intense foreshocks and a slow slip event preceded the 2014 Iquique Mw 8.1 earthquake

Artículo de publicación ISIThe subduction zone in northern Chile is a well-identified seismic gap that last ruptured in 1877. The moment magnitude (Mw) 8.1 Iquique earthquake of 1 April 2014 broke a highly coupled portion of this gap. To understand the seismicity preceding this event, we studied the location and mechanisms of the foreshocks and computed Global Positioning System (GPS) time series at stations located on shore. Seismicity off the coast of Iquique started to increase in January 2014. After 16 March, several Mw > 6 events occurred near the low-coupled zone. These events migrated northward for ~50 kilometers until the 1 April earthquake occurred. On 16 March, on-shore continuous GPS stations detected a westward motion that we model as a slow slip event situated in the same area where the mainshock occurred.Chilean National Science Foundation project FONDECYT no.1130636 and S.R. of project FONDECYT no.11130230. This work received partial support from ANR-2011-BS56-017 and ANR-2012-BS06-004 of the French Agence Nationale de la Recherche