Thermal Segmentation, Interplate Coupling Variability, and Fluid Circulation in the Ecuadorian Subduction Zone

In the Ecuadorian subduction zone, Global Navigation Satellite System (GNSS) measurements indicate significant spatial variations in the interseismic coupling of the interplate contact, along with diverse seismic and aseismic slip behaviors. These variations are likely linked to local differences in the thermo-mechanical properties of the Ecuadorian margin. The thermal and rheological characteristics of the subducting Nazca plate depend on multiple factors, including lithology, sediment thickness, fracturing degree, structural heterogeneities, frictional properties, and fluid circulation. Surface heat flow variations provide indirect insights into some of these deep-seated features. Heat flow profiles derived from "Bottom Simulating Reflectors" (BSRs) reveal a clear north-south thermal segmentation of the Ecuadorian margin. These profiles consistently show a decrease in heat flow on the accretionary prism with increasing distance from the deformation front, stabilizing at approximately ~40 mW.m⁻² along the upper slope. However, heat flow values at the deformation front display significant heterogeneity, ranging from ~60 mW.m⁻² to ~160 mW.m⁻². During the SUPER-MOUV campaign, 18 heat flow measurements were collected to address the following objectives: 1- To evaluate the reliability of heat flow estimations derived from BSRs in Ecuador by conducting direct measurements at the margin front, allowing for a comparison between in-situ data and BSR-derived values. 2- To measure heat flow within the trench, a region where BSRs are absent. 3- To assess heat flow on the Nazca plate before subduction, an area also lacking BSRs, for which no heat flow data exist within 200 km of the deformation front, and for which numerous seamounts, potential sites of fluid circulation, have been identified near the Ecuadorian margin.