Abstract:

Submarine gas hydrates are closely related to active tectonics. Recently submarine active tectonics in the northern South China Sea attract much attention because of exploration of submarine gashydrate in the past decades. We descript the features of faults, earthquakes, and volcanic activity and other active tectonics relating to gashydrate. There are three sets of active faults including NE-, NEE-EW-, NW-striking faults in the northern South China Sea, of which NWtrending faults cut the other two groups. Most of these active faults are inherited from preexisting basement faults. NE- and ENE-trending faults are crustal or lithospheric faults. The earthquake distribution is focused on a NE-trending striped region of the northern South China Sea. However, the NW-trending earthquakes are controlled by the Red River strike-slipping fault. Gas chimneys are related to active structures that play an important role of the formation of the gashydrates, as same as the channel which provides the gas to vertically migrate up to the place under appropriate temperature and pressure for gas-hydrate formation. The distribution of volcanic rocks clockwise rotates from east to west. Based on seismic profile, the volcanic rocks are controlled by tensional fault. The distribution of gashydrates in the eastern part is affected by the NW-trending active faults, however, the west is inextricably linked with the submarine landslide.

Key words: northern South China Sea, active tectonics, faults, gas chimneys, earthquake, igneous rock, gas-hydrates