空振データから見た2000年有珠山の噴火活動(<特集>2000年有珠山噴火 (2))

概要

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An infrasonic microphone network detected clear infrasonic pulses associated with the 2000 eruption of Usu volcano, Japan. The pulses were excited at intervals of several seconds and were considered to be excited by phreatic explosions at active craters from the comparison to visual observation from helicopter. Using the records from the infrasonic network, source locations of the pulses could be precisely identified. The amplitude distribution shows strong azimuthal dependence, which is considered as the topographic effect. The frequency and amplitude of the infrasonic pulses reflected the activity of the phreatic eruption and they became lower and smaller with the decline of the phreatic explosions at the active craters.
2002-09-17