The Large 2014 Slow Slip Event in Guerrero, Mexico: New Feature and Possible Triggering of the 18 April Papanoa Earthquake (Mw 7.3).

Tuesday, 23 February 2016: 3:20 PM
Mathilde Radiguet1,2, Hugo Perfettini1,3, Nathalie Cotte1,4, Adriano Gualandi5, Tiphaine Lhomme1, Vlamidir Kostoglodov6, Andrea Walpersdorf1, Bernard Valette1 and Michel Campillo1,2, (1)ISTerre Institute of Earth Sciences, Saint Martin d'Hères, France, (2)Université Joseph Fourier, Grenoble, France, (3)IRD Institute for Research and Development, Marseille Cedex 02, France, (4)CNRS, Paris Cedex 16, France, (5)California Institute of Technology, Geological and Planetary Sciences, Pasadena, CA, United States, (6)Universidad Nacional Autonoma de Mexico, Instituto de Geofisica, Mexico City, Mexico
Abstract:
Since their discovery two decades ago, the importance of slow slip events (SSEs) as a mechanism of strain accommodation in subduction zones has been revealed. Nevertheless, the interplay between slow aseismic slip and large earthquakes occurrence is still unclear.

In this study, we focus on the Guerrero region of the Central American subduction zone in Mexico, where several SSEs have been observed since 1997 by a permanent GPS network. This region is characterized by the presence of a persistent seismic gap, where large slow slip events have been identified in the past, with a recurrence period around 4 years. We investigate the 2014 SSE, which initiated at the beginning of 2014 and lasted 10 months. During this time period, the April 18th Papanoa earthquake (Mw7.3) occurred on the western limit of the Guerrero seismic gap.

We invert the continuous GPS positioning time series using the PCAIM (Principal Component Analysis Inversion Method), to assess the space and time evolution of slip on the subduction interface. To focus on the aseismic processes, we correct the cGPS positioning time series for the co-seismic offsets of the Papanoa earthquake and its major aftershock. Our results show that the slow slip event initiated in the Guerrero gap region, as in the case of previous large slow slip events. The Mw7.3 Papanoa earthquake occurred on the western limit of the region that was aseismically slipping before the earthquake and was likely triggered by the ongoing aseismic slip. After the Papanoa earthquake, the aseismic slip continues and consists of both the ongoing SSE and the post-seismic (afterslip) response of the Papanoa earthquake and its major aftershock (May 8st, Mw6.5).

To assess the specificity of this SSE, we compare its spatio-temporal evolution to the previous large SSEs in that region (2009-2010, 2006, 2002). The comparison reveals that during the 2014 SSE the region of maximum slip is located downdip from the Papanoa earthquake asperity, whereas it was centered eastward, in the Guerrero gap, during previous SSEs. This suggests complex interactions between the 2014 SSE and the Papanoa earthquake: first, the 2014 SSE likely triggered the Mw 7.3 Papanoa earthquake; second, the earthquake and its afterslip probably modified the characteristics of the ongoing SSE.

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