The main part of the Ryukyu Arc consists of the Nansei Syoto (Ryukyu) Trench, the Nansei Syoto Ridge and the Okinawa Trough from east to west. The Nansei Syoto Ridge forms a geanticline of the Ryukyu Arc, and the basement of the Nansei Syoto Ridge consists of Paleozoic rocks and the Shimanto Super-group distributed widely in Southwest Japan. Volcanic activities of green tuff developed in the Eocene and Miocene, and they destroyed the framework of the pre-Tertiary structure. After the middle to late Miocene regression in the Nansei Syoto area, widely spread transgression in the late Miocene to early Pleistocene caused deposits of the Shimajiri Group, consisting mainly of sand, mud and pyroclastics. The sedimentary basin of the Shimajiri Group spread over the Nansei Syoto area, including the Okinawa Trough region. Judging from the sedimentary pattern, the construction of the present Ryukyu Arc started during the sedimentation of the Shimajiri Group in the Pliocene. Uplift of the Nansei Syoto Ridge and subsidence of the Okinawa Trough continued in response to the development of the Nansei Syoto Trench. The volcanic activities on the Nansei Syoto Ridge took place in the Pliocene to early Pleistocene and the middle Pleistocene to Holocene. The Okinawa Trough in the Quaternary is active in tectonics. Step faults form the graben structure in the axis of the southwest Okinawa Trough. Some grabens have mid-knolls of basaltic to rhyolitic rocks. Recent hydrothermally active spots with sulfide chimneys and ores can be observed in the central part of the trough northwest of Iheya Sima.

抄録全体を表示

The ADCP (Acoustic Doppler Current Profiler) has prevailed rapidly as an oceanographic tool to measure velocity structures in the ocean. In spite of the great capability of the ADCP, the oceanographic progress acquired by it until now is not sufficient. The major reasons for this are: 1) There are no textbooks in which physics and technology related to the ADCP measurement are explained comprehensively. 2) Most of the ADCP programs has so far been completed are not designed to be a joint project running under the close cooperation of researchers and engineers. 3) The ADCP measurement from a ship can maintain a good accuracy only through the complicated processes of calibration and data analysis. It is expected that this review paper serves to improve the above situatioon for the ADCP measurement.

抄録全体を表示

I am greatly honored to be awarded the Okada Prize of the Oceanographic Society of Japan for 1994. The present article reviews my works concerning physical processes of air-sea interface and their relation to microwave backscattering from the wind wave surfaces. A series of laboratory studies by the Physical Oceanography Group, Tohoku University has revealed that fine structures of wind-wave surfaces are generated through physical processes of turbulent boundary layers above and below the air-sea interface. Microwave backscattering from the wind wave surfaces are investigated in a wind-wave tunnel by using a X-band microwave scatterometer. Detailed analysis of time series of the backscattered intensity and Doppler spectrum shows the physical processes of microwave backscattering are closely associated with the processes of the wind wave field.

抄録全体を表示