那須野原の地質と地下水
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概要
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Rocks developed in Nasu plain and its circumference, Tochigi Prefecture, are devided in descending order as follows.<BR>1) Holocene.<BR>a) Flood plain deposits, b) 4th terrace gravels.<BR>2) Pleistocene.<BR>a) Brown volcanic ashes, b) 3rd terrace gravels, c) 2nd terrace gravels, d) 1st terrace gravels, e) Higher terrace gravels, f) Lava of Nasu-volcano, g) Kuroiso pyroclastic rocks.<BR>3) Pliocene.<BR>Otahara pumice flow, b) Lava of Takahara-volcano, c) Ainosawa pyroclastic rocks, d) Yanagibayashi gravels.<BR>4) Miocene.<BR>a) JiOhOji mudstone, Takaiwa taffaceous mudstone, c) Sekiya. group.<BR>5) Palaeozoic.<BR>The permeability of water in each of the above mentioned layers is classified as listed below.<BR>Permeable : I) a), 1) b), 2) a), 2) b), 2) c), 2) d), 2) f), 3) b), 3 c).<BR>Imperfectly impermeable : 2) g), 3) a), 3) c), <BR>Impermeable : 4) a), 4) b), 4) c), 5).<BR>The configuration of the surface of imperfectly impermeable to impermeable layers in Nasu plain is determined by methods of the electric prospecting and the test boring. It is lower in the inside than on both sides of the destrict, indicating the impossibility of running out of ground waters from Nasu plain.<BR>The ground water in Nasu plain is supplied by permeated waters due to rains on the mountains and the plain belonging to the catchment area, as well as those derived from waterways and paddy fields.<BR>The quantity of supply amounts to about 8.8<SUP>m3</SUP>/sec. The permeability coefficient of the terrace gravels is 0, 0044 m/sec and the velocity of ground water is 1521 m/day.
- 社団法人 東京地学協会の論文