Sea Floor Topography of Shallow Gas Hydrate Area:Data from Okhotsk Sea

Abstract

Abstract:

Shallow gas hydrates had already been retrieved by gravity corer, busyness fishing net, and submersible machine on the sea floor and in the sediment near to the sea floor. However the formation mechanism of shallow gas hydrate, distribution of shallow gas hydrate, and also the relationship between shallow gas hydrate and sea floor topography still remain unclear. Based on the side scan sonar and sub-bottom profile data from 2006 gas hydrate cruise in the area of Okhotsk Sea, the paper found that shallow gas hydrates closely related to the dome structures. The dome structures were commonly found on the slope, especially along the Middle and Lower Sakhalin Slope which were about several hundred meters wide and several ten meters high. Different from sea floor sand waves and sand ridges, the dome structures were isolated structures but with a slightly longer and lower wing than that of the upper wing. Sub-bottom profile recorder also showed that buried dome structures also very well developed on the slope beneath a 30 cm modern sediment layer. A joint compress stress field from Deryugin basin to the Sakhalin Slope and also from north Sakhalin Slope to the South Sakhalin Slope along the strike slip fault along Sakhalin Slope was the main cause of the formation of the dome structures, and also the main cause of the diapir structures among the dome structures. Acoustic turbidity beneath the diapir structures clearly show the migration of free gases from deep to the gas hydrate stability zone and to the sea water body from the mini crater on top of the dome structure. Gas hydrates were formed due to the availability of free gas within the diapir structures from the bottom of gas hydrate stability zone up to the sea floor.

CLC Number:

P737.1

LUAN Xi-wu,YUE Bao-jing. Sea Floor Topography of Shallow Gas Hydrate Area:Data from Okhotsk Sea[J]. Geoscience, 2008, 22(3): 420-429.

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