Bathymetry data based on multibeam echosounder EM120 was conducted during R/V SONNE cruise SO222 between 09.06.2012 and 30.06.2012 (Leg A) and 04.07.2012 and 18.07.2012 (Leg B) in the Nankai Trough off Japan. The main objective of the cruise was MeBo drilling and long-term monitoring of active mud volcanoes in the northern Kumano Basin, which carry gas hydrates and are overlying an area of high strain. Hydroacoustic work on board aimed at a high spatial coverage of the Kumano Basin and its mud volcanoes. Furthermore, bathymetric mapping revealed additional features in the study area, of which 5 previously unknown mud volcanoes were identified. Additionally, coring with gravity corers and the MeBO drill rig as well as the deployment of CORK observation instruments and an ROV helped to study the activity and products of mud volcanoes in the Kumano Basin. CI Citation: Paul Wintersteller (seafloor-imaging@marum.de) as responsible party for bathymetry raw data ingest and approval. Description of the data source: During the SO222 cruise, the hull-mounted KONGSBERG EM120 multibeam ecosounder (MBES) was utilized for bathymetric mapping as it is able to perform in water depths up to 11,000 m. Two transducer arrays transmit acoustic signals of 11.25 to 12.6 kHz in successive emission-reception cycles. 191 overlapping beams in a 2° (TX) by 2° (RX) footprint form each acoustic ping, resulting in a beam width of maximum 150° across track and 2° along track. For further information on the system, consult https://www.km.kongsberg.com/. The depth of the water column is estimated through the two-way-travel time, beam angle and ray bending due to refraction in the water column by sound speed variations. Combining lateral and center beams secures measurement accuracy practically independent of the beam-pointing angle. During the cruise SO222, the MBES and PARASOUND sub-bottom profiler were continuously acquiring data of about 1500 km track lengths. Two sound velocity profiles (SVP) were calculated based on SEABIRD CTD measurements and applied to the MBES, whereas no SVP was available for the southern Kumano Basin due to strong currents. Responsible person during this cruise / PI: Paul Wintersteller (pwintersteller@marum.de) Chief Scientist: Achim Kopf (a.kopf@marum.de) CR: http://elib.suub.uni-bremen.de/edocs/00103543-1.pdf CSR: https://www2.bsh.de/aktdat/dod/fahrtergebnis/2012/20120280.htm