HR: 0830h
AN: S11C-0297    [PDF]
TI: Variation Of Seismic Wave Velocity Of Sedimentary Rocks With Pressure Increase
AU: * Lin, W
EM: lin@jamstec.go.jp
AF: Deep Sea Research Department Japan Marine Science and Technology Center (JAMSTEC), 2-15 Natsushima-Cho, Yokosuka, 237-0061 Japan
AU: Mikada, H
EM: mikada@jamstec.go.jp
AF: Deep Sea Research Department Japan Marine Science and Technology Center (JAMSTEC), 2-15 Natsushima-Cho, Yokosuka, 237-0061 Japan
AU: Xue, Z
EM: xue@rite.or.jp
AF: Research Institute of Innovative Technology for the Earth, 9-2 Kizugawadai, Kizu-Cho, Kyoto, 619-0292 Japan
AU: Nakamura, T
EM: To.Nakamura@diaconsult.co.jp
AF: Dia Consultants Co. Ltd., 2-272-3 Yoshino-Cho, Kita-Ku, Omiya, 331-8638 Japan
AB: Variations of compressive wave and shear wave velocities of two sandstones, a mudstone and a tuff taken from Japanese Islands and a basin next to Shikoku Island, Japan were determined with increase of static confining pressure conditions. Additionally, variations of both the velocities and variations of amplitude of compressive wave and shear wave were measured in a complete compression process from the initial point of loading to the point of ultimate fracture under triaxial compression on a specimen of Tako sandstone. The compressive and shear velocities of all the four rocks increased with the static confining pressure increased monotonously. The relations between the velocities and the confining pressure were however non-linear, increasing gradients of the velocities decreased as pressure increased. Increment of compressive velocity with the increase from atmospheric pressure to about 20MPa normalized by the initial velocity corresponding to the same rock varied with the different rocks, and ranged from about 10 percent to 30 percent; whereas the increment of shear wave velocity ranged in about 5-20 percent. In the compressive process under a confining pressure 10MPa, the compressive wave velocity in a direction perpendicular to the major stress direction slightly increased as differential stress increases from the initial point to a stress level equal to about 10 percent of ultimate strength, then decreased several percents from the stress level of about 10 percent to the ultimate strength. However, the shear wave velocity almost did not changed in the confining pressure condition. In contrary, variations of the amplitudes of two waves were distinct than those of the velocities. Ratios of amplitude at arbitrary stress level and the amplitude at initial point of loading corresponding to both kinds of the waves were nearly equal to each other, and the ratios decreased about 40 percent from the initial point to the ultimate strength. These results suggested the variations of amplitude may be more sensitive than those of the velocities with the change of stress state.
DE: 5100 PHYSICAL PROPERTIES OF ROCKS
DE: 5144 Wave attenuation
SC: Seismology [S]
MN: 2003 Fall Meeting