Japan Geoscience Union Meeting 2018

Presentation information

[JJ] Evening Poster

S (Solid Earth Sciences) » S-VC Volcanology

[S-VC41] Active Volcanism

Wed. May 23, 2018 5:15 PM - 6:30 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)

[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.