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We carried out investigation of soil temperature at one-meter depth and water quality (water temperature and electric conductivity) to make clear relationship between slope failure and groundwater flow at source area of debris flow in the Tobinosu-dani-A stream, Zentoku, Tokushima, Japan. Furthermore, we investigated water temperature and electric conductivity of springs, at Tobinosu-dani-C stream, boreholes and underflow at Z6 block of Zentoku landslide to grasp the origin of groundwater. The results of our investigations are as follow. The groundwater flows at the source area of Tobinosu-dani-A stream are under flow type, which is flowing from outside of basin. Direction of these flows are Northeast to Southwest, which may be controlled to relative high permeability structure in the bedrock. The slope failure at source area of debris flow in this stream is caused by underflow from North to South.

Many debris flows caused by heavy rainfall have occurred at mountains in crystalline schist area, Shikoku Island, Southwestern Japan. The typical movement form of debris flow caused by heavy rainfall in mountainous area is fluidizing of soil mass from source area of debris flow to down slope (Stream). The debris flow at Tobinosu-dani stream in Zentoku, Nishiiyayama village on 29 June 1999 is this type of movement form. Therefore, it is important to make clear about occurrence mechanism of slope failures at source area of debris flow. Then, we carried out investigations of soil temperature at one-meter depth, water temperature and electric conductivity of springs and boreholes at the source area in the Tobinosu-dani stream and the Zentoku landslide. The results of our investigations are as follow. 1) There are two types of groundwater flows at the source areas of debris flows in the Tobinosu-dani stream that cause slope failure. One type is underflow changed by groundwater flow in deep layers with low value of electric conductivity. The other type is fissure water like groundwater vein-streams from deep layer with one digit higher value of electric conductivity than the underflow. 2) It is presumed that different of value of electric conductivity between underflow and fissure water is based on the different storage time (groundwater pass). Depth of the fissure water supply, especially, is corresponding to the approximate depth of the sliding surface (or bed rock) in the Zentoku landslide.

At 20:57 and 23:09 local time on the 5 March 1987 locally destructive earthquakes of Ms=6.1 and 6.9 shocked the northeastern part of Ecuador. The name Ecuador means the equator in Spanish, and Quito, the capital of this country, is located just 15 km south of the equator. Ecuador is approximately the same size as Japan except for the island of Hokkaido, and its population is approximately 9.4 million. Lt was primarily an agricultural nation until petroleum was discovered in the western Amazon area in 1972. Even with the substantial reduction in the price of petroleum in 1986, 45% of its total exports constituted petroleum. At present, exports other than petroleum consist of agricultural products such as bananas and coffee. Because of damage to its petroleum pipeline, (a major source of the nation's wealth) caused by the many landslides that took place after the 5 March 1987 earthquakes, Ecuador now has an international debt of 9 billion dollars that is a serious burden on its economy. Structural damage done by the earthquake ground motion was slight because the events took place in a mountainous area 80 km east of the comparatively dense populated central basin. The major damage was from landslides and flooding. Flooding occurred several hours after the earthquakes following the collapse of natural dams formed by sliding rocks and soil that barricaded rivers. The Nagano Prefecture-Seibu earthquake of 1984 in Japan had damage characteristics similar to those seen in Ecuador. The number of dead and missing people resulting from the Ecuadorean earthquakes is estimated as being several hundred to several thousand. The Japanese government dispatched a team of three experts (one each from the Ministry of Foreign Affairs, the National Land Agency, and the Japan International Cooperation Agency) to Ecuador to do earthquake reconnaissance. Our group was sent independently by the Ministry of Education. Culture and Science to survey the damage done by these earthquakes and was