15 Years Of Ecuadorian-French Research Along The Ecuadorian Subduction Zone

Abstract:

The Ecuadorian segment of the Nazca/South America subduction zone is an outstanding laboratory to study the seismic cycle. Central Ecuador where the Carnegie ridge enters the subduction marks a transition between a highly coupled segment that hosted one of the largest seismic sequence during the 20^thcentury and a ~1200-km long weakly coupled segment encompassing southern Ecuador and northern Peru. A shallow dipping subduction interface and a short trench-coast line distance ranging from 45 to 80 km, together with La Plata Island located only 33 km from the trench axis, allow to document subduction processes in the near field with an exceptional resolution.

Since 2000, a close cooperation between the Institute of Geophysics (Quito), INOCAR (Oceanographic Institute of the Ecuadorian Navy) with French groups allowed us to conduct up to 6 marine geophysics cruises to survey the convergent margin and jointly develop dense GPS and seismological networks. This fruitful collaboration now takes place in the framework of an International Joint Laboratory “Earthquakes and Volcanoes in the Northern Andes” (LMI SVAN), which eases coordinating research projects and exchanges of Ecuadorian and French scientists and students.

This long-term investigation has already provided a unique view on the structure of the margin, which exhibits a highly variable subduction channel along strike. It allowed us to evidence the contrast between creeping and coupled segments of subduction at various scale, and the existence of large continental slivers whose motion accommodates the obliquity of the Nazca/South America convergence. Finally, we could evidence the first Slow Slip Events (SSE) that oppositely to most SSE documented so far, are accompanied with intense micro-seismicity.

The recent support of the French National Research Agency and the Ecuadorian Agency for Sciences and Technology (Senescyt) will enable us to integrate the already obtained results, in an attempt to develop an earthquake forecast model for Ecuador.