Evaluation of Volcanic Activity of Kuchinoerabujima in 2006

IGUCHI, Masato, SAITO, Eiji, TAMEGURI, Takeshi, TRIASTUTY, Hetty, YAMAZAKI, Tomoya

Increase in seismic activity as been repeated beneath the Shindake crater of Kuchinoerabujima volcano in time intervals of 1-2 years since the increase of high-frequency earthquakes in July 1999. Similar seismicity was observed in 2006. Monochromatic events began to occur immediately beneath the Shindake crater in August and the seismicity transferred to low-frequency event in October. In November, high-frequency events were frequently observed. Associated with increase in seismicity, inflation of the ground around the crater was detected by continuous GPS observation and change in magnetic total force indicating uprise of high-temperature volcanic fluid began to be detected. Furthermore, temperature of ground surface became high at the bottom and south of the crater as observed by aerial infrared thermal measurement. The volcanic activity in 2006 was one of the increases of activity, which have been repeated since 1999, however, the following remarkable observation facts should be pointed out. (1) Seismicity of low-frequency and monochromatic events attained the highest level during the observation period since 1992. (2) Inflation of the ground dominantly appeared around the Shindake crater and the location of the pressure source became quite shallow (100 – 200m). (3) Composition of fumarolic gas around the crater has changed, especially SO2 gas.

Evaluation of Volcanic Activity of Kuchinoerabujima in 2006

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