Fluid transport properties in sediments and their role in large slip near the surface of the plate boundary fault in the Japan Trench

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doi: 10.1016/j.epsl.2013.08.052
Author(s): Tanikawa, Wataru; Hirose, Takehiro; Mukoyoshi, Hideki; Tadai, Osamu; Lin, Weiren
Author Affiliation(s): Primary:
Japan Agency for Marine-Earth Science and Technology, Kochi Institute for Core Sample Research, Nankoku, Japan
Marine Works Japan, Japan
Volume Title: Earth and Planetary Science Letters
Source: Earth and Planetary Science Letters, Vol.382, p.150-160. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0012-821X CODEN: EPSLA2
Note: In English. Includes appendices. 63 refs.; illus., incl. sect., 2 tables, sketch map
Summary: Fluid transport properties such as permeability and porosity are significant parameters that affect earthquake generation. We measured the transport properties of shallow sediments sampled around the plate boundary near the Japan Trench during IODP Expedition 343 at confining pressures up to 40 MPa. The permeabilities of samples from the shallow plate boundary fault were very low at 10-20 m2, equivalent to a hydraulic diffusivity of 10-10 m2s-1. Permeability and porosity in the core of the fault zone at the plate boundary were lower than those in the immediately overlying sediments and the surrounding intact sediment, suggesting that the plate boundary fault can act as a barrier for fluid flow. Low permeability and high pore compressibility in the shallow plate boundary fault create a strong potential for dynamic fault weakening due to fluid pressurization with frictional heating, even when the initial shear stress is low. Our investigation supports the hypothesis that thermal pressurization on the fault plane helped facilitate the extremely large slip in the shallow part of the subduction zone during the Tohoku earthquake. As the fault zone has a lower permeability than the surrounding sediments and a higher clay content, pore pressure generation at depth by dehydration of clay minerals can explain formation of the shallow strong patch on the fault more reasonably than continuous fluid influx from the subducting oceanic crust, which does not affect pore pressure at depth in the fault zone. Although there are many possible mechanisms of fault weakening, thermal pressurization can act relatively efficiently as slip begins, even at shallow depths. Therefore our results support the role of thermal pressurization in shallow slip during the Tohoku earthquake. Abstract Copyright (2013) Elsevier, B.V.
Year of Publication: 2013
Research Program: IODP Integrated Ocean Drilling Program
Key Words: 19 Geophysics, Seismology; Clay minerals; Dehydration; Diffusivity; Dynamics; Earthquakes; Expedition 343; Fault weakening; Fault zones; Faults; Heating; IODP Site C0019; Integrated Ocean Drilling Program; Japan Trench; Marine sediments; North Pacific; Northwest Pacific; P-T conditions; Pacific Ocean; Permeability; Plate boundaries; Plate tectonics; Pore pressure; Pore water; Porosity; Pressure; Sediments; Shallow depth; Shear stress; Sheet silicates; Silicates; Stress drops; Subduction zones; Tohoku-Oki earthquake 2011; Transport; West Pacific
Coordinates: N375630 N375630 E1435500 E1435500
Record ID: 2014009465
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands