[M-IS26] Gas hydrates in environmental-resource sciences

[MIS26-05] Survey of methane hydrate off Tokachi, Pacific Ocean

*Satoshi Yamashita¹, Akihiro Hachikubo¹, Hirotoshi Sakagami¹, Masaaki Konishi¹, Kzutaka Tateyama¹, Hirotsugu Minami¹ (1.Kitami Institute of Technology)

Keywords:methane hydrate, Submarine topography, marine sediment

In the sea area around Hokkaido, the existence of bottom simulating reflectors (BSR) has been confirmed off Abashiri, Okushiri Island, Hidaka, and Tokachi. In the Pacific Ocean off Tokachi, the National Institute of Advanced Industrial Science and Technology conducted a seismic survey (GH02) in 2002. When the sound wave cross section obtained by GH02 was examined, gas chimneys and mound topography were confirmed at about 30 points on the survey line. Therefore, we are conducting the seafloor topography and methane plume observation by the multi-beam echosounder and quantitative echo sounder, and the sampling of seafloor sediments in the Pacific Ocean off Tokachi after 2014, using the research training ship "Oshoromaru" owned by the Faculty of Fisheries, Hokkaido University. As a result, methane plumes were confirmed at more than 30 locations with characteristic seafloor topography such as faults. In the 2020 survey, methane hydrate was successfully collected at that one site. We report the relationship between the soil properties of seafloor sediments and the seafloor topography, and the methane plume and the seafloor topography, based on previous surveys off Tokachi.