[SSS04-P61] 3D fluid migration due to complex slab geometries and its implications for short-term slow slip events
Keywords:short-term slow slip events, fluid migration, slab geometry, subduction zones, serpentinite
We construct 3D finite element models based on a theory of two-phase flow, which allows us to consider the movement of matrix and fluid phases at the same time. The location of fluid source is determined based on the computed slab surface temperature. Fluids are assumed to migrate in a thin serpentinite layer just above the slab in the direction sub-parallel to the slab surface by the effects of permeability anisotropy in the serpentinite.
We find that fluids migrate in the maximum-dip direction of the slab by the combined effects of permeability anisotropy and 3D slab geometry. It leads to the concentration of fluid paths where the slab geometry is convex and porosity increases there. Fluid paths diverge and porosity decreases where the slab geometry is concave. These results suggest that the along-arc variation in short-term SSEs can be explained by 3D fluid focusing possibly through changing pore-fluid pressure and/or formation of wet clay minerals.