Preliminary results of this study have been presented in the AGU Fall Meeting 2012 in San Francisco.
In this study we report the observations of a Slow Slip Event (SSE) and a synchronous seismicity occurred in 2009 along a segment of the Nazca/South America subduction zone in northern Peru. The SSE event started in early 2009 and lasted 7 months, involving a maximum trenchward displacement of 14 mm recorded at the permanent station in the Bayovar Peninsula. Modeling of the cumulative surface displacements field show that a shallow patch of of the megathrust interface has slipped up to 45 mm leading to and eq. moment release of an earthquake of Mw=6.7. During this period and abrupt increment of the seismicity rate occurred in the same area. However the cumulative seismic moment of the seismicity only accounts for about 35% of the total geodetic moment released. This observation constitutes one of the first that correlates rupture characteristics with aseismic slip in a subduction zone. I general terms, our results suggest a model where the anatomy of the subduction interface is constituted of small to moderate-size isolated patches of velocity weakening material embedded in a much larger velocity strengthening area which promotes aseismic slip or large post-seismic slip once the small asperities are ruptured.
Authors: Villegas Lanza JC., Nocquet J-M., Chlieh M., Vallée M., Tavera H. and Rolandone F.
IGP, Geoazur, IRD and ISTEP