Crustal deformation associated with the 2011 Shinmoe-dakeeruption as observed by tiltmeters and GPS

摘要

The National Research Institute for Earth Science andDisaster Prevention (NIED) developed volcano observation stationsat the Kirishima volcanic group in 2010. The stations observedremarkable crustal deformation and seismic tremors associated withthe Shinmoe-dake eruption in 2011. The major eruptive activitybegan with sub-Plinian eruptions (January 26) before changing toexplosive eruptions and continuous lava effusion into the summitcrater (from January 28). The observation data combined with GEONETdata of GSI indicated a magma chamber located about 7 km to thenorthwest of Shinmoe-dake at about 10 km depth. The tiltmeter dataalso quantified detailed temporal volumetric changes of the magmachamber due to the continuous eruptions. The synchronized tiltchanges with the eruptions clearly show that the erupted magma wassupplied from the magma chamber; nevertheless, the stations did notdetect clear precursory tilt changes and earthquakes showing ascentof magma from the magma chamber just before the major eruptions.The lack of clear precursors suggests that magma had been stored ina conduit connecting the crater and the magma chamber prior to thebeginning of the sub-Plinian eruptions.