1:45 PM - 2:00 PM
[SSS10-13] Integrated analysis of GNSS data for volcano surveillances in Tohoku region, Japan
Keywords:deformation, GNSS, volcano surveillance, postseismic deformation, Azumayama
GNSS geodesy techniques have been widely applied for monitoring volcanic deformations in the world, for example the 2010 eruption of Eyjafjallajokull, Iceland (Sigmundsson et al., 2010), the 2011 caldera unrest of Santorini, Greece (Newman et al., 2012) and the 2011-2012 eruption crisis of El Hierro, Spain (Lopez et al., 2012). These case studies have deepened our understandings of magma supply system beneath volcanoes. In Japan, several institutes including Japan Meteorological Agency (JMA) has conducted GNSS surveillances in both continuous and campaign styles near active volcanoes whereas Geographical Survey Institute (GSI) has operated GEONET (e.g. Nakagawa et al., 2009) which are widely distributed throughout Japan archipelago and mostly located far from volcanoes. Since in many cases, GNSS data have been analyzed independently by each institute with different strategies using different reference systems, there are rooms to discuss the consistency of the solutions. In order to obtain homogeneous solutions from far field to the vicinity of volcanoes, GNSS data sets of JMA and GSI are combined and analyzed with the same parameters and strategies. It is possible to evaluate whole volcanic system consistently using the combined data set which is sensitive to both the deep and the shallow depths. Bernese 5.2 software (Dach et al., 2013) and IGb08 reference coordinates are used to obtain 24-hours solutions. In Tohoku region, in order to detecting volcanic signals, careful treatments are needed by properly evaluating the effects of postseismic deformation by the 2011 Tohoku Earthquake (e.g. Tobita 2016), the steady plate motions and the seasonal trends (Geirsson et al., 2006). The 2014-2015 volcanic activity of Azumayama on the border of Fukushima and Yamagata prefectures has been analyzed by this study.