JpGU-AGU Joint Meeting 2020

Presentation information

[J] Poster

M (Multidisciplinary and Interdisciplinary) » M-IS Intersection

[M-IS32] Gas hydrate in environmental-resource sciences

convener:Hitoshi Tomaru(Department of Earth Sciences, Chiba University), Akihiro Hachikubo(Kitami Institute of Technology), Shusaku Goto(Institute for Geo-Resources and Environment National Institute of Advanced Industrial Science and Technology), Atsushi Tani(Department of Human Environmental Science, Graduate School of Human Development and Environment, Kobe University)

[MIS32-P06] Characteristics of methane hydrate fields in the southwestern margin of the Yamato Basin, southern Japan Sea

*Naoto Ishida1, Hidefumi Fujioka2, Hitoshi Tomaru3, Takao Ebinuma1, Ryo Matsumoto4 (1.Social Systems and Civil Engineering, Graduate School of Engineering, Tottori University, 2.Tottori Prefectural Fisheries Experiment Station, 3.Department of Sciences, Chiba University, 4.Gas hydrate Labratory, Meiji University)

Keywords:shallow-type methane hydrate, Yamato Basin, Japan Sea

The Yamato Basin is one of the methane hydrate fields located in the southern part of the Japan Sea. In the southwestern margin of the Yamato Basin, gas chimneys have been detected by the shallow-type methane hydrate survey conducted by METI. Subsequent researches by the Gas Hydrate Research Laboratory of the Meiji University and Tottori Prefecture revealed characteristics of the methane hydrate fields using sub-bottom profiling, piston and gravity coring, geothermal measuring, interstitial water analysis etc.

Geothermal gradient was measured at the southwestern slope of the basin as 71.33 mK/m and base of gas hydrate stability was estimated to be 138.6 mbsf. Several huge gas chimneys, hundreds of meters in width, were found in the northwestern slope of the Oki Ridge. Carbonate concretions just below the seafloor and shallow (<2.4 m) sulfate-methane interface (SMI) depths around the gas chimneys indicate high methane flux and strongly suggest large volumes of methane hydrate in the gas chimneys.