期刊
JOURNAL OF VOLCANOLOGY AND GEOTHERMAL RESEARCH
卷 178, 期 1, 页码 1-9出版社
ELSEVIER SCIENCE BV
DOI: 10.1016/j.jvolgeores.2007.10.010
关键词
volcano; Sakurajima; Suwanosejima; Semeru; explosive eruption; explosion earthquake; ground deformation
资金
- Ministry of Education, Culture, Sports, Science, and Technology of Japan [14080205]
- Grants-in-Aid for Scientific Research [14080205] Funding Source: KAKEN
A common sequence of phenomena associated with volcanic explosions is extracted based on seismic and ground deformation observations at 3 active volcanoes in Japan and Indonesia. Macroscopic inflation-related ground deformations are detected prior to individual explosions, while deflations are observed during eruptions. Precursory inflation occurs 5 min to several hours before eruption at the Sakurajima volcano but, just 1-2 min at Suwanosejima and 3-30 min at the Semeru volcano. The sequence commences with minor contraction, which is detected by extensometers 1.5 min before eruption at Sakurajima, as a dilatant first motion of the explosion earthquakes 0.2-0.3 s before surface explosions at Suwanosejima, and as downward tilt 4-5 s prior to eruption at the Semeru volcano. The sequence is detected for explosive eruptions with >0.1 mu rad tilt change at Sakurajima, 90% at Suwanosejima and 75% at Semeru volcanoes. It is inferred that the minor contraction is caused by a volume and pressure decrease due to the release of gas from a pocket at the top of the conduit as the gas pressure exceeds the strength of the confining plug. The subsequent violent expansion may be triggered by sudden outgassing of the water-saturated magma induced by the decrease in confining pressure. (C) 2007 Elsevier B.V. All rights reserved.
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