Large Afterslip with Episodic Slip Acceleration following the Mw 7.8 Perdernales Earthquake, Ecuador

International audienceWe analyze continuous GPS measurements along the central Ecuador subduction segment to quantify three years of postseismic deformation that followed the Mw 7.8 April 16 2016 Pedernales earthquake. We perform a kinematic inversion solving for the daily slip along the subduction interface to retrieve the afterslip evolution through space and time. In a previous study (Rolandone et al., 2018), we had found that the early first-month of postseismic period shows large and rapid afterslip developing at discrete areas of the subduction interface. These discrete patches, north and south updip of the coseismic rupture, correlate with areas that had hosted Slow Slip Events in years prior to the 2016 earthquake. In the 3-year postseismic time period, we find that large slip continues at both locations, decreasing through time. Regardless of whether they were locked or not before the earthquake, these areas appear to persistently release stress by aseismic slip throughout the earthquake cycle. Furthermore, our models suggest that modulations of slip rate occur within those areas, with episodes of slip acceleration, sometimes associated with the occurrence of moderate size earthquakes. Aside these patches, afterslip developed updip the coseismic rupture between the patches and downdip of the coseismic rupture, with little slip occurring within the coseismic rupture. During the three years, the cumulative moment released by afterslip is as much as the moment seismically released by the Pedernales earthquake. Therefore, aseismic slip through SSE and afterslip, has a large contribution to the slip budget at the Ecuadorian subduction interface