Modeling seismically induced deformation and fluid flow in the Nankai subduction zone

Fluid pressure changes induced by seismic strains in the Nankai subduction zone were investigated through numerical modeling. Seismic strains resulting from dislocations along fault surfaces were coupled to pore pressure generation, and subsequent transient fluid flow was simulated. This study is distinct from previous efforts that modeled homogeneous systems. Effects of variable mechanical and hydrologic properties were investigated by assigning different mechanical and hydrological properties to marine sediments, the decollement zone, and the upper oceanic crust. Model sensitivity studies suggest that for a reasonable range of parameter scenarios, transient pressure head signals caused by discrete dislocations of a few meters in the updip region of the seismogenic zone can be observed over large areas of the margin from within shallow depths of the sediment wedge to the oceanic crust below the decollement.