Regional network analysis of GPS data in the area of Kanto, central Japan

In order to monitor the crustal deformation in the area of eastern Kanto, central Japan, Ibaraki University has started the high precision geodetic studies with GPS measurements in collaboration with Geographical Survey Institute of Japan (GSI). The first measurements were taken in 1991 with a small network of 8 sites. Four more sites were included since 1998 for a better coverage in the region. In the present study, we analyzed the data collected since 1998 by using the GAMIT/GLOBK software for estimating the displacement vectors in the ITRF96 reference frame. The data from the continuous GPS network of GSI and the GPS sites of IGS close to the studied region (Tsukuba and Usuda) were included for obtaining the primary solutions. The initial results by constraining the co-ordinates of the IGS stations nearest to the network confirmed the repeatability of the baseline components. The results presented here were obtained by assuming the 4 fiducial stations around the network, namely, Irkutsks (IRKT), Fairbanks (FAIR), Sheshan (SHAO) and Dededo (GUAM). The average uncertainties of the horizontal velocities from three consecutive campaigns, each separated by six months, were estimated to be +/-4.6 mm/yr and +/-3.5 mm/yr for the northward and eastward components, respectively.