Details
- Dr. Juan Pablo Canales, Woods Hole Oceanographic Institution (WHOI)
- Date: May, 25, 2016 12:00 am
- Place: Aula Magna de la Facultat de Geologia (UB)
- Location: Carrer de Martí i Franquès, s/n, Barcelona
- Further information: Dr. Antonio Villaseñor (ICTJA-CSIC)
Abstract
Water carried by down-going slabs and their progressive dehydration at depth govern many of the process occurring at subduction zones, such as rheology and dynamics of the mantle wedge, generation of arc magmas, and the aseismic and seismogenic behavior of the plate interface. At the Cascadia subduction zone observations interpreted as resulting from slab dehydration suggest that the Juan de Fuca (JdF) plate is significantly hydrated, contrary to predictions based on its warm thermal structure. Despite its importance for understanding subduction processes beneath this heavily populated region of North America, the hydrated state of the JdF plate remains unconstrained. Here we present water content estimates for the JdF plate prior to entering the subduction zone derived from an active-source seismic tomography profile sub-parallel to the Cascadia deformation front. We find that most of the water is stored at upper crustal levels, with larger hydration associated with high-porosity basement highs and pseudofaults. The lower crust and mantle are nominally dry (except locally at pseudofaults) offshore Washington, and their water content increase southward by 3-2.5 fold, respectively, between 46°N-45°30’N latitude due to increased faulting induced by bending stresses. The along-margin variations in hydration state of the JdF plate correlate with the segmentation of some of the characteristic of the Cascadia margin.