天ヶ瀬地殻変動観測室における坑内温度の精密観測

Abstract

First, the thermal profile along the tunnel at Amagase crustal movement observatory hasbeen observed with a portable thermometer of the thermistor type. The tunnel has a horse-shoe shape with a cross section of 6 mX 6 m and its total length is about 1830 m. Three par-tition walls exist at positions of 5 m, 400 m and 500 m, from the entrance of the tunnel, respec-tively. Temperature distribution in the tunnel is different from 15.2 C to 16.8 C in propo-tion to the depth from the surface.Secondly, temperature changes at several positions in the tunnel have been continuouslyobserved with quartz thermometers having a resolving power of 1/1000 C. Annual change ofthe order of 0.2 C is observed at the position of 370 m from the entrance of the tunnel. Atpositions deeper than the second partition wall existing at 400 m, annual changes of temperatureare smaller than 0.1 C.It is found that there is a direct correlation between short period variation of atmosphere-ic pressure and temperature observed in the tunnel.