長野県大町市周辺地域におけるGPS観測(1993-1994)

概要

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For the purpose of detecting the crustal deformation associated with the seismic activity, interferometric GPS measurements have been carried out at and around Omachi city, the northern part of Matsumoto basin, Nagano, central Japan. The Omachi GPS network, established at and around Omachi, consists of three observation stations, Takaseiri, Miyamura, and Omine stations. Five GPS campaigns were conducted in November 1993, April, July, September, and November 1994. Each campaign consisted of consecutive a few days with a daily two and a half hours session under a good satellite configuration, using single frequency receivers, Trimble 4000SL and 4000SE. The observed data were analyzed using the broadcast ephemerides and the default metorological values by the double difference technique. From the present GPS measurements, it was found that the Miyamura station moved to the southwestward at the rate of about 10 mm (1 ppm strain)/year during the period from November 1993 to Novembver 1994, when the coordinates of Takaseiri station were fixed. This value was larger than the average strain rate 0.2-0.3 ppm strain/year during the last 80 years in the central Japan by about four times. While, at the Omine station, a significant crustal deformation was not detected in the present study.
信州大学の論文