The Tertiary mudstone landslide slope around Ohoike pond in Itakura Town, Niigata Prefecture is complicated geologic structure characterized by the prevalence of faults and small landslides. The strata of slope may be divided into fresh mudstone, weakly weathered mudstone, moderately weathered mudstone, strongly weathered mudstone and colluvial deposit from color and texture of boring core and N values. The groundwater vein-streams run off throuth colluvial deposit, strongly weatherd mudstone and moderately weathered mudstone. The underground temperature survey reveals three groundwater vein-streams; the West groundwater veinstream, the Center groundwater vein-stream and the East groundwater vein-stream. The gamma-ray spectrometry reveals the NNE direction fault system and NE direction faults system.The NNE direction fault system consist of the West fault, the Central fault and the East fault.The points of radon concentration anomalie of soil-gas coincide with back-scar, side-scar and cracks of foot part of small landslide configurations. From the relationships of the distribution of groundwater vein-steams, fault and fissure zone of combination of the back-scar and side-scar of small landslides, it may be inferred as follows; (1) The West groundwater vein-stream runs off through the passage of crack caused by the West fault. (2) The Center and the East groundwater vein-streams run off through the passages of fissure zones.
In order to study hydrogeological problems such as land subsidence and groundwater pollution by organic chlorine compounds in Tama District, the west part of Tokyo Metropolis, Tokyo Metropolitan Government made 18 stratigraphical drillings from 1972 to 1991 which were from 402m to 1, 003m in depth. As the result of this inverstigation, the basal Pre-Tertiary rocks were found at the deep underground in the westernmost part of Musashino Terrace, Mizuho town, Tachikawa city, Musashimurayama city, Akishima city and Hachiouji city. The Quaternary sediments covering these rocks with unconformity are divided stratigraphically into two groups: the lower is the Kazusa Group, and the upper the Tokyo Group. The Kazusa Group comprises the Kitatama Formation and Higashikurume Formation, in ascending order, the Tokyo Group comprises the Toneri Formation and the Edogawa Formation. The Kitatama Formation of the Kazusa Group, the geological oldest sediments discussed here, is developed throughout the Musashino Terrace and consists chiefly of impermeable massive silty layer. On the other hand, formations overlying the Kitatama Formation consist chiefly of permeable sand and gravel layers, and so acts as confined aquifers in this area. The geologic structure of the most western part in the Musashino Terrace is rather different from the east one. In the most western part, the structure of each formation undulates between two axes elongating parallel to the NW-SE trend. It is ascribed to the two reverse faults named Tachikawa Fault and Mizuho One.
Evapotranspiration must be evaluated for analyzing in detail the moisture movement below ground surface which covered with plants. A new equipment for measuring the evaporation or evapotranspiration has been developed. The accuracy of the evaporation measurements has been successfully examined. This technique can be applied to measure the evaporation with high accuracy. Evapotranspiration from three kind of plants as well as the evaporation from water and soil samples were experimentally studied with changing the humidity condition, the temperature condition and the wind condition. It was clearly found that the evapotranspiration from these plants was not so much influenced by those conditions as compared with the evaporation from water and soil. This nature may imply that the evapotranspiration has been controlled by these plants. Field measurement has been performed in two different places at the same time, the first place had vegetation and the second place had no vegetation. Evapotranspiration from the vegetation field was larger than evapotranspiration from the no vegetation field. The transient change of the measured evaporation rate was almost parallel to the change of net radiation.