Earth Planets Space, Vol. 65 (No. 6), pp. 517-525, 2013
Hideki Ueda, Tomofumi Kozono, Eisuke Fujita, Yuhki Kohno, Masashi Nagai, Yousuke Miyagi, and Toshikazu Tanada
National Research Institute for Earth Science and Disaster Prevention, Tennôdai 3-1, Tsukuba-shi, Ibaraki-ken 305-0006, Japan
(Received October 12, 2012; Revised January 8, 2013; Accepted March 2, 2013; Online published July 8, 2013)
The National Research Institute for Earth Science and
Disaster Prevention (NIED) developed volcano observation stations
at the Kirishima volcanic group in 2010. The stations observed
remarkable crustal deformation and seismic tremors associated with
the Shinmoe-dake eruption in 2011. The major eruptive activity
began with sub-Plinian eruptions (January 26) before changing to
explosive eruptions and continuous lava effusion into the summit
crater (from January 28). The observation data combined with GEONET
data of GSI indicated a magma chamber located about 7 km to the
northwest of Shinmoe-dake at about 10 km depth. The tiltmeter data
also quantified detailed temporal volumetric changes of the magma
chamber due to the continuous eruptions. The synchronized tilt
changes with the eruptions clearly show that the erupted magma was
supplied from the magma chamber; nevertheless, the stations did not
detect clear precursory tilt changes and earthquakes showing ascent
of magma from the magma chamber just before the major eruptions.
The lack of clear precursors suggests that magma had been stored in
a conduit connecting the crater and the magma chamber prior to the
beginning of the sub-Plinian eruptions.
Key words: Shinmoe-dake, Kirishima volcano, tiltmeter, volcanic earthquake, volcanic tremor, eruption, crustal deformation, magma chamber.