HR: 1340h
AN: T13B-0471    [Abstracts]
TI: Numerical Modeling of Steady State Pore Pressures and Coseismic Pressure Changes at the Nankai Margin off the Kii Peninsula, Japan
AU: * Screaton, E
EM: screaton@ufl.edu
AF: Dept. Geological Sciences, University of Florida, Box 112120, Gainesville, FL 32611 United States
AU: Hays, T
EM: troyhays@ufl.edu
AF: Dept. Geological Sciences, University of Florida, Box 112120, Gainesville, FL 32611 United States
AU: Ge, S
EM: ges@colorado.edu
AF: Dept. Geological Sciences, University of Colorado, Campus Box 399, Boulder, CO 80309 United States
AB: The Nankai Trough Seismogenic Zone Experiment (NanTroSEIZE) has been proposed to examine subduction zone earthquake generation through drilling and related studies off the Kii peninsula, Japan. A preliminary step in the NanTroSEIZE initiative is fluid flow modeling of the accretionary complex. Previous fluid flow models developed for Nankai have focused on the Muroto transect. Different geometry and heat flow in the Kii transect region calls for new efforts in investigating its fluid flow system. Furthermore, the Kii transect is expected to have underthrust turbidite deposits that may greatly influence fluid flow, whereas the Muroto transect does not. In this study, fluid flow modeling was conducted to assess the potential influence of the underthrust turbidites on pore pressures and to examine coseismic pore pressure changes. Steady-state modeling results suggest that underthrust turbidites can allow drainage and thus greatly influence pore pressures within the underthrust sediments. In a second part of the study, coseismic strain due to slip was calculated using an analytical earthquake strain model. Changes in fluid pressure were then calculated using matrix bulk compressibility and added to the steady-state background pressures. Results suggest that slip on the decollement creates a small, but potentially observable, response relative to background excess pore pressures in the prism. In contrast, slip located seaward of the deformation front, as was inferred for September 2004 earthquakes, has a large effect relative to the near-hydrostatic background excess pore pressures on the incoming plate.
DE: 5114 Permeability and porosity
DE: 8045 Role of fluids
DE: 8104 Continental margins: convergent
SC: Tectonophysics [T]
MN: Fall Meeting 2005