Japan Geoscience Union Meeting 2018

Presentation information

[JJ] Poster

S (Solid Earth Sciences) » S-VC Volcanology

[S-VC41] Active Volcanism

Wed. May 23, 2018 1:45 PM - 3:15 PM Poster Hall (International Exhibition Hall7, Makuhari Messe)

convener:Yuta Maeda(Nagoya University), Takahiro Miwa(National research institute for earth science and disaster prevention), Yosuke Aoki(東京大学地震研究所, 共同), Takeshi Nishimura(Department of Geophysics, Graduate School of Science, Tohoku University), Takahiro Ohkura(Aso Volcanological Laboratory, Institute for Geothermal Sciences, Graduate School of Science, Kyoto University), Satoshi Okumura(Division of Earth and Planetary Materials Science, Department of Earth Science, Graduate School of Science, Tohoku University), Tomofumi Kozono(Department of Geophysics, Graduate School of Science, Tohoku University)

[SVC41-P44] Crustal deformation and volcanic earthquakes associated with the 2008-2011 Shinmoe-dake eruption

*Jun Oikawa1, Hiroshi Munekane2 (1.Earthquake Research Institute, University of Tokyo, 2.Geospatial Information Aurhotiry of Japan)

Keywords:volcanic earthquake, expansion of magma reservoir, magma process lead to volcanic eruption

Kirishima volcanic chain is one of the active volcanoes in southern Kyushu, Japan and is categorized into a composite volcano whose active vents are Shinmoe-dake and Ohachi. The latest eruptive activity of Shinmoe-dake started on August 22, 2008. Subsequently, it erupted on March 30, April 17, May 27, June 27 and 28, and July 5 and 10, 2010. In 2011, the eruption started on January 19 included subplinian and vulcanian explosions. and was followed by sub-Pulinian eruption on 27 January. Eruptive activity gradually ceased since February 2, and moved to Vulcanian activities.
Hypocenter distributions around Kirishima volcano group indicates intense seismic activity under Shinmoe-dake, Ohachi, western and northern area of Karakuni-dake. Figure shows daily number of earthquakes from July, 2008 to January, 2011 around Shinmoe-dake (a), western and northern area of Karakuni-dake (b). Figure (c) indicates the crustal deformation around the western area of Karakuni-dake. Before the 2011 eruption, an inflated crustal deformation around the western area of Karakuni-dake started after the end of 2009. By GPS observation, the inflation source is found at the depth of 8-9km beneath the point of about 5 km WNW-ward from the summit crater of Shinmoe-dake (Nakao, S., et. al., 2013). The total volume charged at the source is estimated 21 million cubic meters under the assumption of Mogi’s model. The seismic activity around Shinmoe-dake became high at the same time the crustal deformation started, we interpret that the pressure change at the magma reservoir caused both ground deformation and elevated seismic activity.