松代地盤隆起型地すべりについて

Abstract

The Makiuchi landslide and the Gongenyama landslide had occurred at Matsushirotown, Nagano city, in Sept. 17 and Oct. 9, 1966 respectivelly. These areas where thelandslides occurred are situated at the middle part of the Matsushiro earthquake swamwhich effect on the faults, cracks, spring discharges and upheaval of crustal block.These landslides are very rare one for its clasifications, therefore we are studying naturalradioactivity survey and chemical analysis were carried out to explain the mechanismsof these landslide occurrence.Natural radioactivity of near cracks and faults from 2.5 x 10'm7/h to 6.2 x 10'm7/himplys being of active faults and hotspring activity. Farther more we continue this su-rvey to explain that the faults and cracks and hot spring activity are increasing or notby the natural radioactivity variations.Chemical analysis of the water samples from the springs which recently gushed outwas carried Out in relation to pH, Na~, Ca", Mg'~, HCO, , C1, SO4~, and solubleSiOz. The wide variation of the content of each ion from 10mg/I to 3, 000mg/I suggeststhat these water samples contain the highly mineralized water from the great depths.The concentration of ions in the spring water increased several times from Septemberto October but the increasing rate varies with the kind of ions. Therefore thevariation of the concentration of each ion can not be explained solely by the dilutionof the mineratized water by the surface water.