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|Title: ||Origins and Saturation of the Hydrate-Bearing Sediments from Seismic Imaging in the Northernmost South China Sea|
|Authors: ||Tan K. Wang;Jia-Ming Deng;Ben-Jhong Yang;Bo-Cheng Gao;Chao-Shing Lee;Char-Shine Liu|
|Contributors: ||NTOU:Institute of Applied Geosciences|
|Keywords: ||continental slope;free gas;pre-stack depth migration|
|Issue Date: ||2011-10-20T08:18:48Z
|Publisher: ||Proceedings of the 7th International Conference on Gas Hydrates (ICGH 2011)|
|Abstract: ||abstract:Horizon velocity analysis and pre-stack depth migration of 468-channel reflection data collected by R/V Marcus Langseth in 2009 and travel-time inversion from four-component data of 61 ocean-bottom seismometers (OBS) recorded in 2007 and 2009 were implemented for imaging P-wave and S-wave velocities of the hydrate-bearing sediment in the northernmost South China Sea. In the overriding wedge off SW Taiwan, high P-wave velocity of 2-2.1 km/s, low Poisson’s ratio of 0.45-0.46 and the largest thickness of about 0.2 km were observed from the hydrate layer whereas low P-wave velocity of 1.4-1.6 km/s, high Poisson’s ratio of 0.47-0.48 and largest thickness of about 0.15 km along the free-gas layer were imaged. The lateral variation of the anomalous velocities indicates the highest hydrate saturation of about 30% and the highest free-gas saturation of about 4% below anticlinal or thrusted ridges and within the sedimentary strata of the thrusted footwall. OBS imaging of the deep sediment (P-wave velocity of 2-3.5 km/s) enables us to identify sources of the gas (or the low-velocity zone) and the gas migration through the major thrusts. In the continental margin of the northern South China Sea, higher P-wave velocity (2-2.2 km/s and 1.5-1.7 km/s) but smaller thicknesses (0.1 km) of the hydrate and free-gas layers were obtained. However, due to the different composition of the sediment, saturation of hydrate and free-gas layers in the continental margin and in the overriding wedge are similar. Velocity variation of the deep sediment (2-3.5 km/s) and the acoustic basement (3.5-4.5 km/s) imaged from OBS data also show how the gas has migrated from the sources to the hydrate-bearing sediment below the erosional ridge and the distal slope in the continental margin of the northern South China Sea.|
|Appears in Collections:||[應用地球科學研究所] 演講及研討會|
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