HR: 1340h
AN: T33D-0597    [Abstracts]
TI: Velocity Structure of Oceanic Crust and the Moho of the Pacific Plate Near Ogasawara Seamount: Insight From Seismic Reflection Data
AU: * Tsuji, T
EM: tsuji@ori.u-tokyo.ac.jp
AF: Ocean Research Institute, the University of Tokyo, 1-15-1 Minamidai, Nakano-ku, Tokyo, 164-8639 Japan
AU: Nakamura, Y
EM: saru@ori.u-tokyo.ac.jp
AF: Ocean Research Institute, the University of Tokyo, 1-15-1 Minamidai, Nakano-ku, Tokyo, 164-8639 Japan
AU: Tokuyama, H
EM: tokuyama@ori.u-tokyo.ac.jp
AF: Ocean Research Institute, the University of Tokyo, 1-15-1 Minamidai, Nakano-ku, Tokyo, 164-8639 Japan
AU: Coffin, M
EM: mcoffin@ori.u-tokyo.ac.jp
AF: Ocean Research Institute, the University of Tokyo, 1-15-1 Minamidai, Nakano-ku, Tokyo, 164-8639 Japan
AU: Matsuoka, T
EM: matsuoka@earth.kumst.kyoto-u.ac.jp
AF: Graduate school of Engineering, Kyoto University, Yoshida hon-machi, Sakyo-ku, Kyoto, 606-8501 Japan
AU: Koda, K
EM: koda-keita@jogmec.go.jp
AF: JOGMEC, 2-2-2, Uchisaiwai-cho, Chiyoda-ku, Tokyo, 100-8511 Japan
AB: Imaging structures within oceanic crust and Moho geometry using multichannel seismic reflection data has been difficult because of challenges in determining accurate velocities within oceanic crust. To obtain improved velocity models, we apply seismic attribute analysis to Common Mid Point (CMP) gathers. We calculate the instantaneous phase from the CMP gather, use the phase information for velocity analysis, and determine velocity models for oceanic crust. We apply this method to seismic reflection data acquired near Ogasawara seamount, with the result of clear images of structures within oceanic crust and the Moho. Furthermore, we use the velocity models to determine depth to Moho. From structures observed in the depth section and our velocity model, we estimate the velocity of Layer 2 to be from 3900 to 5900 m/s, and of Layer 3 to be from 5500 to 7100 m/s. Furthermore, the Moho reflection may be caused by gradual or steplike changes in acoustic impedance. The characteristics of Moho reflections suggest magmatic intrusions near the seamount.
DE: 0902 Computational methods: seismic
DE: 0910 Data processing
DE: 3000 MARINE GEOLOGY AND GEOPHYSICS
DE: 3025 Marine seismics (0935, 7294)
DE: 7220 Oceanic crust
SC: Tectonophysics [T]
MN: Fall Meeting 2005