地学雑誌
Online ISSN : 1884-0884
Print ISSN : 0022-135X
火山で生じる異常現象と近隣地域で起きる大地震の関連性
その事例とメカニズムにかんするレビュー
小山 真人
著者情報
ジャーナル フリー

2002 年 111 巻 2 号 p. 222-232

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Previous studies have reported many examples of possible mechanical coupling between volcanic unrests and large earthquakes, which occurred around the volcano. This paper reviews these studies and reorganizes the types of mechanical coupling into the following five cases (cases A-1, A-2, B-1, B-2, and C) and 10 mechanisms :
In case A-1, in which a large earthquake triggers activation of a volcano, the following four mechanisms can explain their coupling : (A-1-1) an increase in compressional stress, which was produced by earthquake source faulting, squeezes magma up to the surface; (A-1-2) an increase in differential stress (or magma pressure), which was produced by earthquake source faulting, promotes dike intrusion; (A-1-3) increase in tensional stress, which was produced by earthquake source faulting, triggers gas bubbling in magma; and, (A-1-4) dynamic stress change, which was associated with seismic wave, triggers gas bubbling in magma.
In case A-2, in which a large earthquake triggers deactivation of a volcano, the following three mechanisms can explain their coupling : (A-2-1) increase in compressional stress, which was produced by earthquake source faulting, chokes a vent or prevents gass bubbling in magma; (A-2-2) decrease in differential stress (or magma pressure), which was produced by earthquake source faulting, prevents dike intrusion; and, (A-2-3) increase in tensional stress, which was produced by earthquake source faulting, drains magma back toward a chamber.
In case B-1, in which a volcanic unrest triggers a large earthquake, coupling can be explained by mechanism B-1-1 : change in stress, which was produced by dike intrusion (or pressure change in a magma chamber), promotes earthquake source faulting. In case B-2, in which a volcanic unrest prevents a large earthquake, coupling can be explained by mechanism B-2-1 : change in stress, which was produced by dike intrusion (or pressure change in a magma chamber), prevents earthquake source faulting.
In case C, in which a change in plate motion causes a stress change and then triggers (or prevents) a large earthquake (or a volcanic unrest), coupling can be explained by mechanism C : stress change promotes (or prevents) earthquake source faulting or ascending / intrusion of magma.

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