Velocity Structure in Marine Sediments with Gas Hydrate Reflectors in Offshore SW Taiwan, from OBS Data Tomography

Terrestrial, Atmospheric and Oceanic Sciences

关键词: Gas hydrates;    OBS seismic data;    Seismic tomography;    Methane migration;   

DOI  :  10.3319/TAO.2006.17.4.739(GH)

来源: DOAJ

【 摘 要 】

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 offshore 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 up thrust faults. The feature of relatively high P-wave velocity could be considered a result of local shall owing 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.

【 授权许可】

Unknown