飛騨山脈西穂高岳のGPS地殻変動観測（1994－2007）

Since 1994, crustal deformation in northern Nagano Prefecture, including the Hida mountain range, has been measured by a geodetic survey using the Global Positioning System (GPS). The GPS network, established at Nishihotaka-Dake, Hida mountains, and in the Matsumoto Basin along the Itoigawa-Shizuoka Tectonic Line, consists of three observation stations, Kurio (Nishihotaka-Dake), Hakuba (Hakuba village), and Shinshu University (Matsumoto city). The observed data are analyzed from broadcast ephemeris and default meteorological values using the double difference technique. From the present GPS measurements, it has been found that, for the baseline between Kurio and Shinshu University, which is about 34 km in length in the east-west direction, the temporal change of baseline length during thirteen years from 1994 to 2007 showed a contraction of －4cm (－1ppm). Variations of upheaval at Kurio, Nishihotaka-dake, were almost zero during the same period, when fixed at Shinshu-University (Matsumoto city). On the other hand, at the baseline between Kurio and Hakuba, which is about 53 km in the northeast-southwest direction, the temporal change of baseline length showed an extension of ＋5cm (＋1ppm) during the twelve years from 1995 to 2007. And, at the baseline between Hakuba and Shinshu University, which is about 51 km in the northwest-southeast direction, the temporal change of baseline length showed a contraction of －5cm (－1ppm) during the same period. Crustal deformation in northern Nagano Prefecture, including the Hida mountains during the last thirteen years, 1994－2007, are reported and discussed in the present study