Fluids, lithology and structure are known to play a major role in shallow fault slip modes but there is a major issue: Does one of them take precedence over the other two or are they linked ? Are really fluids a key parameter? 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. Thanks to three campaigns at sea and years of onshore/offshore data acquisition, this project 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. To reach this ambitious objective, we will : 1) quantify the fluid content and lithospheric structure by 2D and 3D seismic and heat flow mapping of physical properties of rocks, 2) characterize fluids flowing through the margin by relating fluid seepages to crustal deformation and interplate slip behaviour, 3) detect and locate seismic and transient signals activity with regard to fluids and slip behavio