松本盆地のGPS地殻変動観測（1992－2006）

概要

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Since 1992, geodetic measurements with GPS have been conducted in the Matsumoto basin, Nagano Prefecture, central Japan. The Matsumoto basin is located on the Itoigawa-Shizuoka Tectonic Line, which has recently been considered to be a plate boundary between the Eurasian plate and the North American plate. The GPS network of Shinshu University, established along the Itoigawa-Shizuoka Tectonic Line, consists of six observation stations-Shinshu University, Muroyama, Nakayama, Takaseiri, Miyamura, and Omine. The observed data were analyzed from broadcast ephemeris and default meteorological values using the double difference technique. From the present GPS measurements, it was found that during the period from 1992 to 2006, in the southern part of the Matsumoto basin, the distance between Muroyama and Shinshu University, about 12km in the east-west direction, contracted at a rate of －1mm/year (－0.1ppm/year). On the other hand, in the northern part of the Matsumoto basin, the distance between Omine and Takaseiri about 11km in the east-west direction, contracted at a rate of －5mm/year (－0.5ppm/year) in almost the same period. Crustal deformation in the Matsumoto basin, northern Nagano Prefecture, during the last fourteen years, 1992－2006, are reported and discussed in the present study.