Three dimensional seismic studies of deep-water hazard-related features on the northern slope of South China Sea |
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| Institution: | 1. Key Laboratory of Marine Geology and Environment, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China;2. University of Chinese Academy of Sciences, Beijing 100049, China;3. School of Earth, Atmospheric and Environmental Sciences, University of Manchester, Manchester M13 9PL, UK;4. MARUM, Center for Marine Environmental Sciences, University of Bremen, Bremen 28359, Germany;5. CNOOC, Research Institute, Beijing 100027, China;1. Key Laboratory of Tectonics and Petroleum Resources, China University of Geosciences, Ministry of Education, Wuhan 430074, China;2. Laboratory for Marine Mineral Resources, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266061, China;3. College of Marine Science and Technology, China University of Geosciences (CUG), Wuhan, Hubei 430074, PR China;4. Natural Resources Canada, Geological Survey of Canada (Atlantic), Bedford Institute of Oceanography, P.O. Box 1006, Dartmouth, Nova Scotia, B2Y 4A2, Canada;5. Shenzhen Branch of CNOOC Ltd., Guangzhou 510240, China;6. Sanya Institute of Deep-sea Science and Engineering, Chinese Academy of Sciences, Sanya 572000, China |
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| Abstract: | Mass transport deposits and geological features related to fluid flow such as gas chimneys, mud diapirs and volcanos, pockmarks and gas hydrates are pervasive on the canyon dominated northern slope of the Pearl River Mouth basin of the South China Sea. These deposits and structures are linked to serious geohazards and are considered risk factors for seabed installations. Based on high resolution three dimensional seismic surveys, seismic characteristics, distributions and origins of these features are analyzed. A distribution map is presented and geometrical parameters and spatial distribution patterns are summarized. Results show that various groups of the mapped features are closely tied to local or regional tectonism and sedimentary processes. Mass transport complexes are classified as slides near the shelf break, initially deformed slumps on the flanks of canyons and highly deformed slumps on the lower slope downslope of the mouth of canyons. We propose them to be preconditioned by pore pressure changes related to sea level fluctuations, steep topography, and fluid and fault activities. Gas chimneys are mainly located in the vicinity of gas reservoirs, while bottom-simulating reflectors are observed within the gas chimney regions, suggesting gas chimneys serve as conduits for thermogenic gas. Mud diapirs/volcanos and pockmarks are observed in small numbers and the formation of pockmarks is related to underlying gas chimneys and faults. This study aims at reducing risks for deep-water engineering on the northern slope of South China Sea. |
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| Keywords: | Deep-water hazard-related features Mass transport complexes Fluid flow Gas hydrate Gas chimney Mud volcano Pockmark South China Sea |
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