焼岳における精密水準測量による傾斜観測(1977-1979)

抄録

A small aperture (20-65 m) bench mark array for spirit-level survey has been installed on Yake-Dake Volcano in October 1977. The levelling net which is located 0.5 km from the main active fumarole, consists of three loops, with a total length of 529 m. Spirit level surveys have been annually conducted in Oct. 1977, Sept. 1978 and Oct. 1979. Loop closures afford a precision of about 0.5√mm (D; loop length, km). Tilt vector from 1977 to 1979 shows a dip of about 10μradians/year towards NNW which means a relative upheaval of the sumit of Yake- Dake.