GPS constraints on the 2013 Oaxaca slow slip event: Implications for slow slip and postseismic afterslip interactions
Monday, 22 February 2016: 12:55 PM
Shannon E Graham, Harvard University, Earth and Planetary Sciences, Cambridge, MA, United States, Charles DeMets, University of Wisconsin Madison, Madison, WI, United States, Robert McCaffrey, Portland State University, Portland, OR, United States, Enrique Cabral-Cano, UNAM National Autonomous University of Mexico, Departamento de Geomagnetismo y Exploración, Instituto de Geofísica, Mexico City, Mexico, Vladimir Kostoglodov, UNAM National Autonomous University of Mexico, Mexico City, Mexico, Andrea Walpersdorf, ISTerre Institute of Earth Sciences, Saint Martin d'Hères, France and Nathalie Cotte, CNRS, Paris Cedex 16, France
Abstract:
Less than one year after the 20 March 2012 Mw=7.4 Ometepec earthquake, a slow slip event (SSE) occurred on the Oaxaca portion of the Mexico subduction zone. This was the first SSE following the Ometepec earthquake and its considerable postseismic afterslip, thus creating a unique opportunity to study possible interactions between afterslip and slow slip. We use measurements from 41 continuous GPS stations throughout southern Mexico to determine the location, magnitude, and temporal evolution of slow slip during the 2013 SSE. Viscoelastic deformation as a result of the 2012 earthquake is approximated with a 3-D finite element model and subtracted from the observations. We then use TDEFNODE to invert for the evolution of slip from the day after the earthquake through the 2013 SSE, modeling both the postseismic afterslip and the SSE in order to account for any continued afterslip during the SSE. Preliminary results show slow slip originating on the eastern side of the afterslip region with slip migrating outward to the historical Oaxaca SSE region. The 2013 SSE represents a possible example of postseismic afterslip dynamically evolving into or triggering slow slip.
