HR: 0800h
AN: T51A-1326    [Abstracts]
TI: The relationship between pore-pressure and the elastic-wave velocities of TCDP-cores
AU: * Kitamura, K
EM: keigo-kitamura@aist.go.jp
AF: GSJ, AIST, Central-7, Higshi1-1-1, Tsukuba, 305-8567 Japan
AU: Takahashi, M
T51A-1326 AF: GSJ, AIST, Central-7, Higshi1-1-1, Tsukuba, 305-8567 Japan
AU: Masuda, K
T51A-1326 AF: GSJ, AIST, Central-7, Higshi1-1-1, Tsukuba, 305-8567 Japan
AU: Ito, H
T51A-1326 AF: JAMSTEC, Showa-machi 3173-25, Kanazawa-ku, Yokohama, 236-0001 Japan
AU: Song, S
T51A-1326 AF: National Taiwan University, No.1, Sec. 4, Roosevelt Road, Taipei, 106 Taiwan
AU: Wang, C
T51A-1326 AF: National Central University, No.300, Jhongda Rd., Jhongli, 32001 Taiwan
AB: The elastic-wave velocities and the permeability of fault-related rocks are essential keys to reveal the earthquake process. We measured these parameters of boring-cores of the Chelungpu-fault (TCDP-cores) that is the earthquake-source fault of the 1999 Chi-Chi earthquake in Taiwan under high-pressure conditions. Experimental apparatus we used is the gas-medium, high-pressure and high-temperature deformation apparatus at the AIST Japan. We measured elastic-wave velocities and permeability simultaneously with decreasing pore-pressure (Pp) from 20 to 0 MPa under the constant confining-pressure and temperature condition (30 MPa and 25C). We measured compressional-wave velocities (Vp) and shear-wave velocities (Vs) at once. We adopted the oscillation method to measure the permeability because this method can measure the low-permeability with relatively short time, under high pore pressure conditions. We obtained 18 experimental cylindrical specimens sized 20 mm in diameter and 20 mm long, sampled from 482 m to 1316 m depth of the TCDP-core archives (mainly silty-sandstone and sandstone). It would be the first report to refer a relation between these physical properties of porous sediments. The results of our elastic-wave velocities measurement indicate the strong effect of pore-pressure on elastic-wave velocities. They increased rapidly with decreasing Pp down to 10 MPa. The elastic-wave velocities didn_ft change with decreasing Pp from 10 to 0 MPa. All samples showed similar pore pressure- velocity curves but different ratios of dV/dPp. It is considered that the volume of pores and crack decreased with decrease of pore-pressure. It can be said the pressurization effect on the elastic wave velocity would reflect significantly on the bulk density of sedimentary rocks. The Vp- and Vs-values decreased successively from silty-sandstone to sandstone at low-Pp condition (10-0 MPa). These results indicate that the Vp- and Vs-values are controlled by lithology under low-Pp conditions. On the other hand, Vp- and Vs-values show no clear reation to the lithology under over-hydrostatic-pressure conditions (Pp=10-20 MPa). Permeability decreased logarithmically with decreasing Pp in this experimental conditions. We can discuss the relationship between shape and volume of pores and physical properties of sedimentary rocks using these results.
DE: 5100 PHYSICAL PROPERTIES OF ROCKS
DE: 5102 Acoustic properties
DE: 5112 Microstructure
DE: 5114 Permeability and porosity
DE: 5194 Instruments and techniques
SC: Tectonophysics [T]
MN: Fall Meeting 2005