Friction experiments on saturated sediments and their implications for the stress state of the Nankai and Barbados subduction thrusts

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doi: 10.1016/S0025-3227(03)00286-X
Author(s): Kopf, A.; Brown, K. M.
Author Affiliation(s): Primary:
Scripps Institution of Oceanography, La Jolla, CA, United States
Volume Title: Marine Geology
Source: Marine Geology, 202(3-4), p.193-210. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0025-3227 CODEN: MAGEA6
Note: In English. 68 refs.; illus., incl. sects.
Summary: The Nankai and Barbados forearcs have low-stress subduction thrusts. The sediments entering the subduction zone, and namely the material in the décollement zones, have been well characterized by numerous deep-sea drilling legs and studies of the recovered cores. Nankai has high heat flow and significant amounts of illite, while Barbados is a smectite-dominated system. Based on results from ring shear (<2 MPa normal stress) and direct shear (<30 MPa) tests on marine sediments and mineral standards, this translates into a residual frictional resistance of µr = ∼0.25 and µr = ∼0.11 in clay horizons, respectively. Such values agree with theoretical estimates from critical wedge theory (Nankai: µb = ∼0.16-0.26 and Barbados: µb = ∼0.06-0.09) and fault spacing geometries from seismic profiles (Nankai µb = ∼0.12-0.23 and Barbados: µb = ∼0.11-0.19). Maximum pore pressure ratios of λ = 0.85 and 0.73 for Nankai and Barbados, respectively, allow us to estimate effective shear stresses as a function of friction coefficient and density of the sediment gouge to reach only ∼10 MPa or less in the frontal ∼50 km of the décollement zone, respectively. Our data support the contention that fluid pressure transients and sediment composition contribute equally to the weakness along plate boundary faults down to the seismogenic zone, with the first probably dominating the shallow décollement. Shear velocity stepping tests show that the clay-dominated gouges strengthen velocity irrespective of the clay mineralogy, and hence suggest that clay transformation does not affect the onset of seismogenesis. Abstract Copyright (2003) Elsevier, B.V.
Year of Publication: 2003
Research Program: ODP Ocean Drilling Program
Key Words: 07 Marine Geology and Oceanography; 18 Geophysics, Solid-Earth; Accretionary wedges; Antilles; Atlantic Ocean; Barbados; Caribbean region; Controls; Decollement; Experimental studies; Faults; Fluid pressure; Friction; Gouge; Island arcs; Lesser Antilles; Marine sediments; Nankai Trough; North Atlantic; North Pacific; Northwest Pacific; Ocean Drilling Program; Pacific Ocean; Philippine Sea Plate; Plate boundaries; Plate tectonics; Pore pressure; Saturated materials; Sediments; Seismicity; Seismotectonics; Shear; Shear stress; Soil mechanics; Standard materials; Stress; Subduction zones; Tectonics; Thrust faults; Troughs; West Indies; West Pacific
Record ID: 2004007665
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands

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