Origin of Gas Hydrates Imaged from the Acoustic Basement in the Northernmost South China Sea by Using OBS

Abstract

During the survey of TAiwan Integrated GEodynamics Research (TAIGER) in 2009, we recovered 36 ocean-bottom seismometers (OBS) along 3 multi-channel seismic (MCS) profiles for investigating the origin of gas hydrates in the northernmost South China Sea off SW Taiwan. In the accretionary prism of the Manila subduction zone, we observed gas hydrates accumulated in the closed areas where were formed by folding imaged from a strong variation of the lateral velocity (3-4.5 km/s) in the acoustic basement. In the continental slope, gas was migrated from the rifting basement to the anticline. The rifting basement with a relatively low velocity of 3-4.5 km/s in the extended continent of the northernmost South China Sea resulted from magma intrusion along normal faults since the paleo-seafloor spreading. We suggest that gas generated in the deeper structures may be migrated along faults to accumulate hydrates in the sedimentary layers.