|Title:||Velocity Structure in Marine Sediments with Gas Hydrate Reflectors in Offshore SW Taiwan, from OBS Data Tomography||Authors:||Cheng, Win-Bin
|Keywords:||Gas hydrates; Methane migration; OBS seismic data; Seismic tomography||Issue Date:||2006||Journal Volume:||17||Journal Issue:||4||Start page/Pages:||739-756||Source:||Terrestrial, Atmospheric and Oceanic Sciences||Abstract:||
In the fall of 2004, four profiles of a total length of about 80 km and 24 recovered Ocean Bottom Seismometers (OBSs) were acquired along off-shore southwestern Taiwan. These profiles were oriented in E-W and N-S directions to map the velocity structure of sediments by modeling the vertical component of OBS data. The thickness of sedimentary layers ranges from a few hundred meters to about 2 km, with the largest thickness being found beneath ridges. The most striking feature in the velocity models along E-W profiles is the relatively high velocity wedges, extending from the seafloor to about 2 km in depth; these could be interpreted as a series of westward upthrust faults. The feature of relatively high P-wave velocity could be considered a result of local shallowing of the base of the gas hydrate stability zone, caused by ascending flows of deep fluids passing through the fault zone. In the N-S profiles, a dome-like high velocity structure was observed and could be associated with the phenomenon of hydrate/gas phase boundary fluctuation. After erosion, the sub-seafloor temperature gradient redistributes and results in the hydrate/gas phase boundary moving downward. The results obtained in this study show that tectonic control is an important factor in determining bottom-simulating reflector (BSR) distributions offshore of southwestern Taiwan.
|DOI:||10.3319/TAO.2006.17.4.739(GH)||SDG/Keyword:||marine sediment; numerical model; seafloor; seismic data; seismic reflection; seismic tomography; seismometry; tectonic setting; temperature gradient; velocity structure
|Appears in Collections:||海洋研究所|
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