摘要：Since the caldera-forming eruption of Miyakejima Volcano in 2000, low-frequency (LF) earthquakes have occurred frequently beneath the caldera.Some of these LF earthquakes are accompanied by emergent infrasonic pulses that start with dilatational phases and may be accompanied by the eruption of small amounts of ash.The estimated source locations of both the LF earthquakes and the infrasonic signals are within the vent at shallow depth.Moreover, the maximum seismic amplitude roughly correlates with the maximum amplitude of the infrasonic pulses.From these observations, we hypothesized that the infrasonic waves were excited by partial subsidence within the vent associated with the LF earthquakes.To verify our hypothesis, we used the infrasonic data to estimate the volumetric change due to the partial subsidence associated with each LF earthquake.The results showed that partial subsidence in the vent can well explain the generation of infrasonic waves.
