[S-VC54_1AM2] Volcanic and igneous activities, and these long-term forecasting

[SVC54-11] Forming process of Minamidake stratovolcano, Sakurajima, inferred from paleomagnetic age and volume of lava flows

*Daisuke MIKI¹ (1.DPRI, yoto University)

A paleomagnetic measurement was carried out on the Arimura lava, which consists uppermost part of the main body of Minamidake stratovolcano, Sakurajima volcano, Kyushu, Japan. A mean paleomagnetic direction, D=4.0⁰E I=40.5⁰down, was obtained from the Arimura lava. By comparison between measured paleomagnetic direction and the paleo-secularvariation of geomagnetic field, the age of the Arimura lava was estimated as about 3.1-2.7 ka, moreover the age of the Kannonzaki lava lying beneath the Arimura lava, was thought as about 3 ka. These two lavas are considerable to be formed by a sequence of intermittent eruption during several hundred years at around 3 ka. The volumes of individual lava that extruded in recent 4,000 years were estimated. The main body of Minamidake stratovolcano had grown rapidly at around 3 ka, since estimated lava volume. The volume of the Nagasakihana lava erupted in 764-766 AD was estimated as about 0.8km³. The scale of 764-766 AD eruption may be greater than previously thought. The long?term magma effusion rate during historic time, particularly recent 240 years, was estimated as larger than earlier.