Downward shift of gas hydrate stability zone due to seafloor erosion in the eastern Dongsha Island, South China Sea

New acquired and reprocessed three-dimensional (3D) seismic data were used to delineate the distribution and characterization of bottom simulating reflections (BSRs) in the Chaoshan Sag, in the eastern part of Dongsha Island, South China Sea. Three submarine canyons with different scales were interpreted from the 3D seismic data, displaying three stages of canyon development and are related with the variation of BSR. Abundant faults were identified from the coherence and ant-tracing attributions extracted from 3D seismic data, which provide the evidence for fluid migration from deeper sediments to the gas hydrate stability zone (GHSZ). The uplift of Dongsha Island created a large number of faults and leads to the increased seafloor erosion. The erosion caused the cooling of the seafloor sediments and deepening of the base of the gas hydrate stability zone, which is attributed to the presence of paleo-BSR and BSR downward shift in the study area. Hence, methane gas may be released during the BSR resetting and gas hydrate dissociation related with seafloor erosion.