HR: 1340h
AN: S43B-0999    [Abstracts]
TI: Acoustic Velocity Of The Sediments Offshore Southwestern Taiwan
AU: Tsai, C
EM: goodrrooyy@sinamail.com
AF: Institute of Oceanography, National Taiwan University, Institute of Oceanography, National Taiwan University, Taipei, P.O. Box 23-13, Taiwan 106, Taiwan, ROC, TAIPEI, 106 Taiwan
AU: * Liu, C
EM: csliu@ntu.edu.tw
AF: National Center for Ocean Research, Taipei 106, Taiwan, ROC, TAIPEI, 106 Taiwan
AU: Huang, P
EM: meulen@earth.sinica.edu.tw
AF: Institute of Oceanography, National Taiwan University, Institute of Oceanography, National Taiwan University, Taipei, P.O. Box 23-13, Taiwan 106, Taiwan, ROC, TAIPEI, 106 Taiwan
AB: Along the Manila Trench south of 21›XN, deep-sea sediments are being underthrusted beneath the Taiwan accretionary prism which is composed of the Kaoping Slope and Hengchun Ridge. Offshore southwestern Taiwan, foreland sediments and Late Miocene strata of the Tainan Basin are being accreted onto the fold-and thrust belt of the syn-collision accretionary wedge of the Kaoping Slope. The Kaoping Slope consists of thick Neogene to Recent siliciclastics deformed by fold-and-thrust structures and mud diapers. These Pliocene-Quaternary sediments deposited in the Kaoping Shelf and upper slope area are considered to be paleo-channel deposits confined by NNE-SSW trend mud diapiric structure. Seismic P-wave velocities of the sediment deposited in the Kaoping Shelf and Kaoping Slope area are derived from mutichannel seismic reflection data and wide-angle reflection and refraction profiles collected by sonobuoys. Sediment velocity structures constrained from mutichannel seismic reflection data using velocity spectrum analysis method and that derived from sonobuoy data using tau-sum inversion method are compared, and they both provide consistent velocity structures. Seismic velocities were analyzed along the seismic profile from the surface to maximum depths of about 2.0 km below the seafloor. Our model features a sediment layer1 with 400 ms in thickness and a sediment layer2 with 600 ms in thickness. For the shelf sediments, we observe a linear interval velocity trend of V=1.53+1.91T in layer1, and V=1.86+0.87T in layer2, where T is the one way travel time within the layer. For the slop sediment, the trend of V=1.47+1.93T in layer1, and V=1.70+1.55T in layer2. The layer1­Ýs velocities gradients are similar between the shelf (1.91 km/sec2) and the slope(1.93 km/sec2). It means layer1 distributes over the slope and shelf widely. The result of the sediment velocity gradients in this area are in good agreement with that reported for the south Atlantic continental margins.
DE: 0902 Computational methods, seismic
SC: Seismology [S]
MN: 2004 AGU Fall Meeting