New high-resolution 2D seismic imaging of fluid escape structures in the Makran subduction zone,Arabian Sea |
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| Institution: | 1. Key Laboratory of Marine Mineral Resources, Ministry of Natural Resources, Guangzhou Marine Geological Survey, Guangzhou 510760, China;2. Key Laboratory of Gas Hydrate, Ministry of Natural Resources, Qingdao Institute of Marine Geology, Qingdao 266071, China;3. Laboratory for Marine Mineral Resources, Qingdao National Laboratory for Marine Science and Technology (Qingdao), Qingdao 266071, China;4. National Institute of Oceanography, Karachi 75600, Pakistan;5. Key Laboratory of Submarine Geosciences and Prospecting Techniques, MOE, Ocean University of China, Qingdao 266100, China |
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| Abstract: | Seabed fluid escape is active in the Makran subduction zone, Arabian Sea. Based on the new high-resolution 2D seismic data, acoustic blanking zones and seafloor mounds are identified. Acoustic blanking zones include three kinds of geometries: Bell-shaped, vertically columnar and tilted zones. The bell-shaped blanking zone is characterized by weak and discontinuous reflections in the interior and up-bending reflections on the top, interpreted as gas chimneys. Vertically columnar blanking zone is interpreted as side-imaged gas chimneys associated with focused fluid flow and topped by a seafloor anomaly expressed as a localized reflection discontinuity, which may together serve as a vent structure. Tilted acoustic blanking zone could be induced by accretionary thrust activity and rapid sedimentation surrounding slope. Seafloor mounds occur at the sites of bell-shaped acoustic blanking zone and may be associated with the material intrusion. Bottom simulating refectors (BSRs) are widely distributed and exhibit a series of characteristics including diminished amplitude, low continuity as well as local shoaling overlapping with these acoustic blanking zones. The large amount of gases dissociated from the gas hydrates migrated upwards and then arrived at the near-seafloor sediments, followed by the formation of the gas hydrates and hence the seafloor mound. |
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| Keywords: | Makran Fluid escape structure Gas hydrate Gas chimney Seafloor mound Marine geological survey engineering Pakistan Arabian Sea |
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