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Large Gas Reservoir Along the Rift Axis of a Continental Back‐Arc Basin Revealed by Automated Seismic Velocity Analysis in the Okinawa Trough
Author(s) -
Mukumoto Kota,
Tsuji Takeshi,
Hendriyana Andri
Publication year - 2019
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2019gl083065
Subject(s) - geology , rift , trough (economics) , hydrothermal circulation , seismology , structural basin , petrology , seafloor spreading , geomorphology , geophysics , economics , macroeconomics
In the Okinawa Trough off southwestern Japan, hydrothermal circulation due to back‐arc rifting is active. Biogenic CH 4 in discharging hydrothermal fluids at the Iheya North Knoll is derived from outside the knoll; however, the location of the gas reservoir has not been identified. Here, we applied automated velocity analysis to seismic reflection data to obtain a P wave velocity structure in high spatial resolution. The resulting profiles reveal large gas reservoirs as low‐velocity zones along the rifting axis (>5 km for axis direction) around the Iheya North Knoll. The main gaseous components in the reservoir could be CO 2 and CH 4 . The heat flow inferred from seismic profiles (i.e., depth of reflector) indicates that CH 4 hydrate could be trapping the gas. Furthermore, the heat flow is higher at the rifting axis and close to the knoll, reflecting the large gas reservoir feeding the hydrothermal fluids in the discharging area at the knoll.