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Department of Earth Sciences

Seminars and Events

How do faults in accretionary wedges grow?

24th October 2017, 12:00 to 13:00, Arthur Holmes Building - ES230 -TR3, Dr. Rebecca Bell - Lecturer in Geology and Geophysics, Imperial College London

Over the last couple of decades, we have learned that a whole spectrum of different fault slip behaviour takes place on subduction megathrust faults from stick-slip earthquakes to slow slip and stable sliding. Pore fluid pressure has been implicated as a potential regulator of slip behaviour. Intra-wedge thrust faults represent important conduits for fluid flow in accretionary wedges, and may play a key role in modulating pore fluid pressure, effective stress and, ultimately, the seismic hazard potential of convergent plate boundaries. However, our understanding of the geometry and evolution of intra-wedge thrusts is limited, and as such, so too is our appreciation of their permeability structure and impact on fluid flow. To address this, I will present observations from two subduction zones, the Nankai and Lesser Antilles margins, where 3D seismic and borehole data allow us to constrain the geometry and kinematics of intra-wedge fault networks and to thus shed light on the mechanisms responsible for their structural style variability. The results reveal that incoming plate properties, including the depth to the Opal CT-quartz transition and basement relief (even when it is blanketed by sediments), have a profound effect on the geometry and evolution of faults in the accretionary wedge. These insights into the controls on intra-wedge fault kinematics provide new hypotheses that can be tested with numerical and laboratory models.

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