T11A-2530: Effects of a Subducting Seamount on the Overriding Plate Deformation and Faulting

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Authors: Min Ding1, Jian Lin2

Author Institutions: 1. Geology and Geophysics, MIT/WHOI, Woods Hole, MA, USA; 2. Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, MA, USA

The goal of this investigation is to test a conceptual hypothesis that a subducting seamount might generate a complex fault system in the upper plate above a subduction interface. We performed a series of finite-element numerical experiments to investigate how the overlying plate deforms and how fault systems develop and evolve. A subducting seamount is modeled as a upward-pointing rigid cone that moves in the direction of plate subduction. We examine the changes in the upper plate elastoplastic deformation as a function of the seamount depth and shape, the dipping angle of the subduction zone, and the plastic failure criteria of the upper plate For all tested models, regions of horizontal extension and normal faults are located in the thinner part of the plate seaward of the seamount, while regions of horizontal compression and thrust faults lie on the thicker part of the plate landward of the seamount. We found that the amount of the seamount movement required for the faults to cut through the entire upper plate is larger for deeper seamounts, for greater dipping angles of the plate, and for the Mohr-Coulomb than the Von Mises failure criteria. It is also noted that the formation of through-going thrust faults requires larger seamount movement than the formation of through-going normal faults. We are in the process of implementing strain-softening rheology to simulate narrow shear-zone-like faults in the upper plate. These numerical models provide new insights into the time-dependent upper plate deformation process during seamount subduction.

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