有珠火山山頂カルデラ内での土壌からのCO_2放出量の連続測定(<特集>2000年有珠山噴火 (2))

概要

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Continuous soil CO_2 efflux measurement was carried out at the southern inner slope of Usu Caldera for about 5 months between May 2000 and October 2000. The result of continuous monitoring showed that temporal variations of atmospheric pressure and precipitation influence the CO_2 efflux at Usu volcano. Peaks of CO_2 efflux were usually observed after the precipitation of more than several mm/hr, which last several hours. We found two main trends of CO_2 flux during the observation period. In the period between June 20 and August 17, we observed decreasing trend of the CO_2 flux, that may be related to decreasing eruptive activity of the 2000 Usu eruption. In the period from September 19 to October 23, the CO_2 flux response was strongly negative-correlated with atmospheric pressure (time lag: 24 hours, γ=-0.74). Two trends of soil fluxes suggest that the degassing mechanism was different between the two periods.
特定非営利活動法人日本火山学会の論文
2002-09-17