Remote sensing study and application in the Geological Survey have twenty years of history back to 1965. They have mostly been done as a part of research work related to geothermal investigation. Among them, three subjects are put lights in this article ; they are, 1) early date case history on aerial thermography, 2) a volcano-geologic study initiated from Landsat image observation, and 3) remote sensing application in the Hohi geothermal area. Aerial thermography represents one of the earliest remote sensing stud y in Japan. Other two are the example that the aspect given by remote sensing investigation has b een taken into account in the following survey including drilling. Research on aerial thermography was started in 1965 and it included the co -research with the Nippon Electric Company on the construction of airborne thermal infrared scanners.The technique was used for regional geothermal survey in 1970s and recent research aims at the quantitative use of the data for more detailed temperature mapping. A large circular feature with 15 km in diameter, newly found in the Landsat image of northern Honshu, has been surveyed since 1978 in view from both volcano -geology and geothermal resources. It was identified to be a half concealed Plio-Pleistocene caldera and named Okiura Caldera. The result of drilling done mostly during 1981 and 1982 for geo-thermal development indicates that the higher temperature portion lies inside the caldera suggesting the influence of magma resurgency. A big national geothermal survey is being conducted in the Hohi geothermal area, north central Kyushu and several remote sensing data were used for the survey. These data include Landsat, airborne SAR, and aerial thermograph as well as conventional aerial photograph. Examples of quantitative evaluation of the aerial thermoraph and field evaluation of a long lineament extracted from the SAR image are introduced in the article. An attempt for structural analysis using digitally processed Landsat data and geophysical data such as gravity and aeromagnetic data is being attempted in the Hohi geothermal area.
Disasters are originated through very complicated processes in which various conditions and causes are interrelated each other. These conditions and causes are distinguished into two categories, namely, primary cause and inducement. The primary cause includes natural and artificial conditions subject to natural hazards, and the inducement means various natural hazardous phenomena to cause disasters. The informations expecting to be obtained from satellite remote sensing are the ones concerning to the above mentioned primary cause and inducement of wide area, periodic or real time nature which are hardly obtained effectively and economically by the traditional means for observation, measurement and investigation. These informations will be very useful for the technological improvement of three important aspects in disaster prevention as follows: the first is watching and forecasting unusual natural phenomena, the second is exact holding the actual state of a disaster and the third is the estimation of a disaster by exact holding primary cause and inducement likely to occur. The significance of satellite remote sensing in the field of disaster prevention exists in the improvement and promotion of scientific and technological capabilities for the three aspects mentioned above. In this report, the author describes various possibilities and expectations on the application of satellite remote sensing in the field of disaster prevention based on many studies carried out or carried on in and outside of country. As to the first aspect, watching and forecasting for storm rainfall and flash flood, snow coverage and thawing, iceberg, huge volcanic eruption and diffusion of volcanic ash cloud into atmosphere, big forest fire, etc. by means of geosynchronous and orbital satellite data are emphasized. Further, the effectiveness of marine observation in the future by means of active remote sensors such as altimeter, scatterometer and synthetic aperture radar is stressed. For the second aspect, some case studies using Landsat MSS data carried out by the author and his colleagues in the National Research Center for Disaster Prevention are mainly described. The studies include detection of the damage of rice fields due to flooding in the lower Ishikari River basin in 1981 and in Kumamoto Plain in 1982, detection of the coverage of volcanic products due to the eruptions of Ontake Volcano in 1979 and of Miyakejima Volcano in 1983, and detection of landslides due to heavy rainfalls and earthquakes occurred during 1978 to 1984. The effectiveness and usefulness of Landsat MSS data are demonstrated by showing the good coincidence of the analytical results with ground truth data. Concerning to the third aspect, the author describes his ideas how to utilize remote sensing data in this aspect in which estimation methods of disasters such as flood, landslide, volcanic eruption and erathquake are outlined. He put an emphasis on the synthetic use of extracted informations from remote sensing data with other various informations necessary for the estimation of disasters.
In spite of such well-known merits as large scope of semi-real-time, periodical digital data image, remote sensing has not come into practical use yet in the field of agricultural land use survey in Japan, not only because of its rough resolution for Japanese arable land and poor cloud condition during main farming season, but also because of insufficient regional theory of agricultural economics which concerns with regional analysis in agricultural area. Generally speaking, agricultural land use survey in Japan has been made for the purpose of understanding evolution of peasant economy through cropping system analysis and therefore it has not necessarily been abound in regional implications. But recently the concept of local agricultural system, which consists of villages as substantial and spatial units of farming, appears to express a significant object of governmental agricultural policy and this goeseespecially for recentepaddy conversion programme. With this change of management theory, agricultural land use survey by village is becomingemore essential for economic land classification which is now rather regionalization by social condition of farming than evaluation of potentiality of land for which it was ordinally intended. Because long-term and nation-wide survey is necessary to map out a new strategy of rice production, remote sensing data can be applied, for the moment, to monitor distribution of paddy conversion. On a techinical point, it is not very difficult to extract paddy field and upland field. According to a case study in this article, Landsat data, which is standerdized on UTM coordinated so that other data and cartographic information including village boundary, can give us general view of land use as well as converted paddy distribution even at village level (Photo 2, Photo 4, Photo 6), and it suggests a possibility to find new factors of land use change through remote sensing data analysis. However estimation of the area by Landsat data differs from seasons and rarely corresponds with census data. Improving quantitative accuracy and stability of seasonal and serial data should be the most urgent problem for forthcoming agricultural land use survey by satellite remote sensing.
The term mass rock creep structure is here used for structures resulted from long -term gravitational rock slope deformation without a continuous sliding surface. Mass rock creep structures have been known implicitly, to be a kind of mass movements, but have been scarcely studied scientifically partly because those have been taken to be of little impor-tance, in geology, to academic research or investigation of mineral resources. The mass rock creep structure, however, is not only important in structural or engineering geology but also important in the technology for natural disaster prevention, because mass rock creep is sometimes a precursor of large landslide. This paper describes a large mass rock creep structure of crystalline schist, which have been only poorly described till now, on a mappable to microscopic scales at Ogai district in the Sambagawa terrain in the Kanto mountainous land. Ogai district is located on a dip slope of a first-order fold, where basement rocks is mainly composed of pelitic schist. The schist, made up of quartz thin layers and pelitic thin layers, is probably originated from chert laminite. The macroscopic investigation on a mappable scale revealed that the rock masses at Ogai district have deformed gravitation-ally and disintegrated into three blocks rotated each upon a vertical axis. The strike trace of bedding schistosity have eventually deformed into box fold-like pattern in a plan view, and a large landslide topography (1 km wide and 1.5 km long) has been formed. This macroscopic mass rock creep occurred at first as the formation of creep zones within the creeping rock mass. The creep zones are those where straining and fracturing of the rock masses due to the mass rock creep are intensive. The creep zones at Ogai district are classified into three groups ; high-angled creep-fracture-zone, low-angled creepfracture-zone, and creep chevron folds. The low angled fracture-zone contains partial, discontinuous, sliding surfaces of the incipient stage. These zones and folds are basically made by slip of small rock masses along schistosity and by fracturing of quartz thin layers. The high-angled creep-fracture-zones as well as low-angled ones, are separated into two parts: phyllitic and massive. The zones contain scarcely clayey materials. The phyllitic and massive parts change to each other gradually. While the high-angled fracture-zone is not sharply bounded with the hanging and foot-walls, the low-angled fracture-zone is sharply bounded only with the hanging wall forming a sliding surface. The creep chevron folds are the type of buckle folds with several to 20cm wavelength. The folds were generated by a compressional force acting parallel to the schistosity of pre-fold stage. Quartz thin layers in the axial part of the folds are fractured intensively and the layers in the limbs have structure resembling pulled-apart structure of sedimentary rocks with the intervening open cracks 5-20μm wide. The mass rock creep structures like those at Ogai district may be very common in the areas where foliated rock masses such as crystalline schist, slate, and chert laminite are distributed.