桜島の噴火と周辺の地殻変動との関係

概要

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The vertical displacement of the earth's crust in the neighbourhood of Sakurazima Volcano at the time of the 1914 great eruption is studied on the basis of the results of precise levelling. This depression of the earth's crust is reasonably explained as the elastic deformation which is caused by the pressure decrease of a spherical pressure source at the depth of 10km from the surface. And this pressure source does not exist under the Sakurazima Volcano, but at the center of Aira Caldera (Kagoshima Bay) 10km north of the Sakurazima crater. The relation between the crustal deformation and the eruption may be considered as follows. Before the eruption, the magma reservoir (pressure source) was at high pressure and the pressure decreased owing to the outflow of lava at the time of eruption. As the result of that, the surface of the earth's crust was depressed . After the eruption, the earth's surface which subsided at the time of the eruption began to rise and the upheaval continued for several years. The phenomenon suggests the increase of pressure of magma reservoir. In addition the writer discussed the close relations between the increase and decrease of the pressure of the lava reservoir and the eruptions of Sakurazimincreosea Volcano.
1957-01-15