Results of the multibeam echo sounder observations on the GB21-2,3 cruises (around Tokara Islands)

Abstract

The high-resolution bathymetry was observed using Multibeam echosounder (MBES) as a part of an ongoing seafloor mapping around Tokara Islands, a region from latitude 28°45' N to 31°15' N, and longitude 128°50° E to 131°20' E. The bathymetry map indicates that several bathymetric highs such as Hiki Sone, Minami-Gama Sone, Gon Sone, and Tairashima Sone, are part of a continuous ridgelike feature and possibly is located on the edge of the Okinawa Trough. The backscatter intensities are relatively high around Kuchinoshima, Nakanoshima, Gajashima, Kogajajima, Suwanosejima islands, and Hiki Sone, which suggest the presence of volcanic collapse depositions around them. Such highbackscatter intensities are also shown around Akusekijima and Tairashima islands suggesting distribution of volcanic collapse depositions, too. The result indicates that volcanic activities accompanied by volcanic collapses is common along the volcanic fronts of the Tokara Islands.