15. 櫻島噴火に伴う音響微動觀測結果

概要

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Observations of the detonations together with the short period tremors, which caused by the eruptions of Sakurazima Volcano, were made at Kaigata, a village across the sea, about 6km SE, of Sakurazima Island, from April 9 to 18, 1946. The both kinds of records, that is to say, detonation records and tremor ones, showed a clear difference between the case of lava ejected and the case of smoke only. In the former case, after a preliminary small amplitude tremors of short period, detonations and somewhat large amplitude tremors of short period appeared on records. [simultaneously, but, in the latter case, no preliminary tremors were recognized on record. It may be explained that the preliminary tremors were exited by lavas which ascended giving slight disturbances to the crater wall. From this result, we should found the travelling time of lava ascending from bottom to upper edge of the crater, and then, if we estimate either the initial velocity of ejective volcanic bombs or the depth of crater, it is possible to know the other. In the present investigations, we made an explanation with the earthsounds phenomena caused by the voloanic activities.
東京大学地震研究所の論文