In this paper, some geomorphological and geological explanations on the survey results of "Basic Map of the Sea (1:50,000)" carried out in coastal water off Saruhutu in June-July 1987, are shown.
Flat planation surfaces are widely distributed on the sea floor except around banks and shoals. Very flat planation surfaces reflecting the ancient water levels are observed at the depths from 15 m to 25 m and from 50 m to 70 m.
Conglomeraric sediments with a very small amount of fine-grained sediments are distinguished in the bottom material under the influence of strong current in the coastal waters.
Seven beds from Is to VIIs are identified in the subbottom geological sections. We suppose many valleys were formed during the last glacial regression age at the basement of Is bed.
Many folds in the north-south direction are distributed at subbottom geological structure. However, tectonic movement during the Quaternary, was not confirmed.
South-easterly current is dominant in the coastal waters.

View full abstract

An underwater sliding vehicle (USA) is a kind of towing instrument with CTD sensors, which can measure continuously temperature and salinity profiles in the upper layer of the upper ocean. The principal features and the advantages are as follows.
The USV moves up and down along a faired cable by the command from the research vessel, when the catenary of faired cable is fixedby the depressor in tow. The vehicle has no need to lift the cable, and therefore, it can move rapidly up and down without rolling.
In order to communicate with the body in underwater, an inductive coupling data communication system was developed. This bidirectional communication system enables us to monitor the oceanic data in real-time, and to control the body motion with a personal computer on board.
In this paper, the characteristics of the body motion obtained in the open sea off Sanriku are shown. And more, the results of comparison between the temperature and salinity data obtained with the USV and with a standard CTD and an ordinary water sampler in the same sea, are expressed.
Finally, it is shown that the USV has a capability of measuring the complicated temperature section in such region as the marginal area of a Kuroshio warm-core ring.

View full abstract

The Multi-Narrow Beam Echo Sounder HS-10 is the first Japanese-made deep sea echo sounding equipment jointly developed by the Japan Marine Science and Technology Center, Kawasaki Heavy Industries, Ltd. and Furuno Electric Co., Ltd. The HS-10 was installed on the Yokosuka, the support ship for the manned submersible Sinkai 6500. A series of experiments was carried out at sea to evaluate its basic performance during the sea trials of the Yokosuka from December 1988 through February 1989.
In these experiments, the HS-10 demonstrated its ability to sound the depths of seamounts ranging from 1,200 to 4,500 m deep as well as the trench bottom of 9,600 m maximum depth.
This paper introduces the main characteristics of the HS-10 and reports on the results of the experiments.

View full abstract

Technology of marine seismic reflection survey has made remarkable progress during the last several decades, mainly with the advances of hydrocarbon exploration and electronics technology.
Developments of multi-channel digital seismic recording systems including streamer cables and bore hole receivers, and of stable long-life seismic sources such as "Water Gun", have improved the survey techniques on board, bringing many new marvelous methods such as three dimensinal survey and vertical seismic profiling.
Processing techniques of digital seismic reflection data have been improved with the advances of the computer technology and the field data acquisition techniques. Though conventional seismic processing needed a very big size of computer with array processor about twenty years ago, it is now possible to process the seismic data more quickly than before by using a small size of mini-computer, due to the progress of the computer technology. Also, increased capacity of the big computer enables us to process a large amount of seismic reflection data, so that various types of processing techniques such as three dimensional processing and wavelet processing have been developed.
Above mentioned techniques have improved the seismic reflection profiles. Then new geological interpretation methods, such as chronostratigraphic analysis of sea level changes, have become possible,

View full abstract

IZANAGI, Oceanfloor Imaging System(OIS), is a 11/12 kHz, long-range, and shallow towed, high-speed side scan sonar system. It produces geometrically correct synoptic acoustic backscatter images and hydrographic-quality swath bathymetry charts in water depths from about 300 to 10,000 meters. The bathymetry charts are produced by using multiple rows of transducers to measure the phase delay (and thus the angle of incidence) at the towed array from all echoes from the seafloor.

View full abstract

Okinawa Radio Wave Observatory develoved the first Japanese HF Ocean Radar in 1988. This radar can observe line-of-sight velocities of ocean surface currents with wide range in a short time. The observable range with the radar extends beyond the visible horizon.
This paper describes the principles and the out line of this system and some results of observation of ocean currents off Okinawa.

View full abstract

It has been the urgent and very strong requirements of marine construction industry to develop a new echo-sounder with the following features:
(1) To be compact and light.
(2) To be economical on consumption.
(3) To be very accurate.
(4) To be easy and simple on operations.
For this purpose, we have adopted a microcomputer aided thermal recording system for the sounding data acquisition and completed the Thermal-Microcomputer Aided Echo sounder.
The author describes, in this paper, on details of the present echo-sounder and the safisfactory results on the aboved-mentioned features conduced by various tests.

View full abstract