Fluids Circulation in Subduction Zones: How Fluids Impact Seismic/Aseismic Slip in Ecuador ?

Identifying the circulation of fluids in subduction zone system and understanding their role on the megathrust fault slip modes remains one of the outstanding challenges in Earth Sciences. As these faults have the capacity to generate mega-earthquakes, the associated hazard to the society is significant.In recent years, studies in Japan, Costa Rica and New Zealand try to find the processes that control slip behaviours through marine campaigns and IODP drillings. The Ecuadorian margin is an exceptional laboratory to continue this international effort by adding a subduction zone to the list of those with contrasted slips at shallow depth. In April 2016, a Mw 7.8 earthquake broke the southern part of the 1906 earthquake rupture zone, causing hundreds of deaths and millions of dollars in damages along an increasingly populated coastline. The seismological and geodetic network in place since several years and a dense post-seismic deployment, contributed to observe and define the rupture zone and areas affected by aseismic slip on the shallowest portion of the megathrust fault.Thanks to two marine campaigns (HIPER and SUPER) and other existing onshore/offshore data acquisition, our project Fluid2Slip will participate to determine the exact role of fluids on slip behaviour around the updip part of the seismogenic megathrust fault by localizing fluids and seismicity, imaging fault properties and deformation. Our large experiment allowed a high density onshore/offshore deployment to perform shots and earthquakes FWI (Full Waveform Inversion) and obtain sufficient resolution to tackle the role of fluids with respect to interplate roughness, the nature of sediments, upper plate and lower plate's structural heterogeneity in seismic/aseismic slip behavior. In addition, subsurface observation and fluid geochemistry will help detect fluid flow and discuss the path they take through the upper plate.