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GEOPHYSICAL RESEARCH LETTERS, VOL. 33, L10304, doi:10.1029/2006GL025737, 2006

Excess pore pressures within subducting sediments: Does the proportion of accreted versus subducted sediments matter?

E. Screaton

Department of Geological Sciences, University of Florida, Gainesville, Florida, USA

Abstract

Although previous numerical modeling studies have examined pore pressures in both accretionary and non-accretionary subduction zones, they have not addressed the question of whether the proportion of accreted versus subducted sediments significantly affects pore pressures. This modeling study used consistent parameters to compare excess pore pressures directly below the decollement for varying proportions of accreted sediment. Within the initial 5 to 12 kilometers arcward of the deformation front, subduction zones with lesser accretion thickness show lower simulated excess pore pressures than those with greater accretion thickness due to the ease of fluid escape when overlying wedge sediments are thin. However, at greater distances arcward of the deformation front, the magnitude of excess pore pressures significantly increases and the excess pore pressures peak further arcward as the proportion of underthrust sediments increases. This difference suggests that the proportion of accreted versus subducted sediment could potentially affect seismogenesis.

Received 11 January 2006; accepted 17 April 2006; published 19 May 2006.

Index Terms: 5104 Physical Properties of Rocks: Fracture and flow; 8104 Tectonophysics: Continental margins: convergent; 8170 Tectonophysics: Subduction zone processes (1031, 3060, 3613, 8413).

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Citation: Screaton, E. (2006), Excess pore pressures within subducting sediments: Does the proportion of accreted versus subducted sediments matter?, Geophys. Res. Lett., 33, L10304, doi:10.1029/2006GL025737.

Copyright 2006 by the American Geophysical Union.