桜島深部の地震活動について

Abstract

Since eraly houre of the 29th of May, 1968, a great many felt earthquakes have occurred.So, the precise seismometric observation using the data-recorder and the other instruments werecarried out.The results of the investigation on these earthquakes can be summarized as follows:I) Supposing that the underground structure is homogeneous and having the averragevelocity of 2 Km/sec. Or 3 Km/sec. For P wave, the epicenters of these earthquakes are estimated tobe distributed from the center to the east part of Sakurajima and to be 2-15 Km deep.2) The push pull distribution of P wave of these earthquakes does not prove any regularity.3) The coefficient of Isbimato-Lida's empirical formula, m, is 1.8 which is equivalent to oneof the deeper zone earthquakes in the volcano.4) Since the occurrence of the eatbquake swarm, the surface phenomena of the volcano havenot shown the conspicious change, and the shallow zone earthquakes near the crater have notoccurred so many too.