[S-CG52] Ocean Floor Geoscience

[SCG52-10] Observation of geology and topography in the Japan Trench off Miyagi using a full ocean depth submersible

*Hayato Ueda¹, Todd Bond³, Paige Maroni³, Hiroshi Kitazato², Alan Jamieson³, science team Pressure Drop Ring of Fire Expedition 2022 Japan Cruise Leg2 (1.Department of Geology, Niigata University, 2.School of Marine Resources and Environment, Tokyo University of Marine Science and Technology, 3.Minderoo-UWA Deep-Sea Research Centre, School of Biological Sciences and Oceans Institute, The University of Western Australia)

Keywords:manned submersible, Japan Trench, full ocean depth

Because many studies suggested that fault rupture of the 2011 earthquake propagated to the surface in the Japan Trench axis, and resultant topographic changes near the trench are thought to have caused the devastating tsunami disaster, it is important to directly observe and visually record the topography and surface geology in and around the trench. However, we have not had the way to access to sea floors of trench axes deeper than 7000 m since the accident of full ocean depth ROV Kaiko in 2003. Therefore, detailed topographic and geological observation and surface mapping in the Japan Trench axial area are left untouched despite many indirect data of echo and seismic soundings and limited core data have been obtained. In September 2022, we had a research cruise (DSSV Pressure Drop Ring of Fire Expedition 2022 Japan Leg 2) to the Japan Trench off Miyagi aiming both biological and geological researches using a full-depth rated manned submarine (DSV Limiting Factor) and unmanned landers. We had three submersible dives to the trench axis (dive #123), lower inner Trench slope (#124), and lower outer trench slope (#125). Although material sampling by its manipulator was unfortunately disabled, we observed topography and outcrops of bottom sediments, obtaining HD video records. We will present preliminary results of geological points of view.