Inflations prior to Vulcanian eruptions and gas bursts detected by tilt observations at Semeru Volcano,Indonesia |
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| Authors: | Takeshi Nishimura Masato Iguchi Ryohei Kawaguchi Surono Muhamad Hendrasto Umar Rosadi |
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| Institution: | (1) Department of Geophysics, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan;(2) Sakurajima Volcano Research Center, Disaster Prevention Research Institute, Kyoto University, Kagoshima 891-1419, Japan;(3) Center for Volcanology and Geological Hazard Mitigation, Bandung, 40122, Indonesia |
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| Abstract: | We examine the basic characteristics of inflations at Semeru Volcano, Indonesia, to clarify the pressurization process prior
to two different styles of explosive eruptions: Vulcanian eruptions and gas bursts. Analysis of data obtained from tilt meters
installed close to the active crater allows clarification of the common features and the differences between the two styles
of eruptions. To improve the signal-to-noise ratio and to determine the mean characteristics of the inflations, we stack tilt
signals obtained from eruptions of different magnitudes and evaluate the maximum amplitude of the seismic signal associated
with these eruptions. Vulcanian eruptions, which explosively release large amounts of ash, are preceded by accelerating inflation
about 200–300 s before the eruption, which suggests volume expansion of the gas phase. In contrast, gas bursts, which rapidly
effuse water steam accompanied by explosive sounds, follow non-accelerating changes of inflation starting 20 s before each
emission. Tilt amplitudes increase with the magnitude of eruptions for both eruption styles. This suggests that the volume
and/or pressure of magma or gas stored in the conduit before eruptions controls the magnitude of volcanic eruptions. These
results further suggest that the magnitude of eruptions can be predicted from geodetic measurements of volcano inflation. |
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