Open AccessTransport properties and dynamic processes in a fault zone from samples recovered from TCDP Hole B of the Taiwan Chelungpu Fault Drilling Project
Author(s) -
Tanikawa Wataru,
Sakaguchi Masumi,
Hirono Tetsuro,
Lin Weiren,
Soh Wonn,
Song ShengRong
Publication year - 2009
Publication title -
geochemistry, geophysics, geosystems
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.928
H-Index - 136
ISSN - 1525-2027
DOI - 10.1029/2008gc002269
Subject(s) - fault gouge , geology , drilling , fault (geology) , scientific drilling , permeability (electromagnetism) , slip (aerodynamics) , pore water pressure , mineralogy , petrology , seismology , geotechnical engineering , thermodynamics , materials science , physics , membrane , biology , metallurgy , genetics
We measured transport properties at a confining pressure of 60 MPa in core samples from the fault zone in Hole B of the Taiwan Chelungpu Fault Drilling Project (TCDP). Permeability and specific storage of the fault gouge range from 3 × 10 −15 to 1 × 10 −17 m 2 and from 2 × 10 −10 to 7 × 10 −10 Pa −1 , respectively, and the measured hydraulic diffusivity was 6 × 10 −5 m 2 /s, which is consistent with the data measured in situ. Numerical analysis of the thermal pressurization mechanism during the 1999 Chi‐Chi earthquake using laboratory measured transport and frictional properties showed that pore pressure at the fault zone increased dramatically during slip, whereas temperature increased only moderately to 400°C at the end of slip. The results indicate that dehydration of interlayer water in smectite is plausibly caused by frictional heating, although such dehydration does not influence fault weakening. The decomposition reactions of other minerals are difficult to explain for only one slip event. A magnetic susceptibility anomaly observed in the fault zone is consistent with the modeling results, although low contents of inorganic carbon and clay minerals are not. We concluded that these inconsistencies can possibly be explained by the combined effects of enhancement of chemical reactions by mechanochemical influences and periodic movement on the Chelungpu fault. High‐temperature water‐rock interactions are also a possible explanation for inconsistencies.