Volcanic tremor

Japanese: 火山性微動 - かざんせいびどう（英語表記）volcanic tremor

A vibration specific to volcanoes that can be detected by a seismometer and is distinguished from earthquakes by its waveform and duration. Unique earthquakes such as low-frequency earthquakes are also a type of volcanic tremor. Earthquakes caused by external factors such as rockfall are excluded. They can sometimes last for several days. They often precede eruptions and are particularly important from the standpoint of predicting eruptions. While earthquakes are a phenomenon that correspond to the destruction of the earth's crust, volcanic tremors are thought to occur in conjunction with the flow of magma and steam, and in the process in which groundwater boils and steam foams in the magma (forming bubbles).

(Yoshiaki Ida, Professor Emeritus, University of Tokyo / 2007)

Source : "Chiezo" published by Asahi Shimbun Publications Co., Ltd. About Chiezo

Japanese:

地震計にとらえられる火山特有の振動で、波形や継続時間から地震と区別される。低周波地震などの特異な地震も、火山性微動の一種。落石など、火山の外部に原因を持つものは除外する。継続時間は、時には数日間にも及ぶ。噴火に先行することも多く、噴火予知の立場からは特に重要。地震が地殼の破壊に対応する現象なのに対し、火山性微動はマグマや水蒸気の流れに伴い、また地下水が沸騰し、マグマ中で水蒸気が発泡(気泡の形成)する過程で発生すると考えられる。

(井田喜明東京大学名誉教授／ 2007年)

出典　(株)朝日新聞出版発行「知恵蔵」知恵蔵について　情報

<<: Volcanic front

>>: Volcanic earthquake