Intermittent inflations recorded by broadband seismometers prior to caldera formation at Miyake-jima volcano in 2000

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• 作者：Tomokazu Kobayashi^a ; ^{tkoba@gsi.go.jp} ; Takao Ohminato^b ; Yoshiaki Ida^c ; Eisuke Fujita^d
• 关键词：Miyake-jima ; very-long-period seismic pulse ; caldera formation
• 刊名：Earth and Planetary Science Letters
• 出版年：2012
• 出版时间：1 December, 2012
• 年：2012
• 卷：357-358
• 期：Complete
• 页码：145-151
• 全文大小：745 K

文摘

Very-long-period (VLP) pulses with widths of 20 s on velocity seismograms were observed during volcanic activity at Miyake-jima Volcano, Japan in 2000. The VLP events occurred repeatedly during a few days prior to caldera formation and essentially vanished following the onset of caldera collapse. Waveform inversions of the pulse-like signals point to a source offset 3.5 km beneath and 1 km south of the summit. A candidate for the source mechanism is the inflation of an elliptical cylinder with axis tilted 20-30¡ã from vertical and major axis of the elliptical cross section oriented northeast-southwest. The inferred mechanism appears consistent with a step-like pressurization of a magma reservoir impacted by a falling rock mass in response to gravitational instability. The repeated occurrences of the rock collapses lead to the caldera formation at Miyake-jima.