14. 櫻島噴火に伴ふ短週期火山微動

概要

論文の詳細を見る
Durling the eruption of Sakura-jima, we observed volcanic tremors of short periods by means of electromagnetic transducers. The magnification of instruments is about 110,000 times for the vibration of 20 cycles. The results of observation are as follows. (i) The frequency of waves is about 20 cycles and kept constant during the observation. This predominant period seems to be independent upon locality, as far as a few places we are concerned. (ii) The velocity is determined by two methods. The one is the determination of time lag between the arrival of wave group and sound of detonation, and the other the determination of phase difference of waves recorded by two transducers which are set about 7 meters distant from each other in the direction to the crator. The results of two methods fairly coincide with each other, the value of velocity being about 300m/sec. (iii) The waves are dispersive. (iv) We observed also two kinds of waves having the frequency of 5 cycles and about 80 cycles. (v) The variation in amplitude of main waves is also observed. It will be concluded from these results that the main waves are a kind of surface waves generated at the crator by the shock of eruption.
東京大学地震研究所,Earthquake Research Institute, University of Tokyo,地震研究所,地球物理學敎室の論文
1948-06-30