Abstract
Global Positioning System (GPS) measurements with Trimble 4000SDs were started at five stations in the southern part of central Japan in September 1988. Baseline lengths in the network range from 22 to 172 km. Observations discussed in this paper have data acquisition times longer than 4 h and were performed during the period from March 1989 to March 1991. Baseline vectors were determined with the broadcast orbit elements of the satellites and the standard atmospheric model data. Strain rates obtained from the present data were (-2.3-1.7)×10-7/year. The strain rates agree with the results obtained by conventional surveys which were carried out during the last 100 years in this region. It was found that GPS measurements for baselines shorter than 100 km are useful to discuss crustal movements with an accuracy of the order of 10-7 even if they are obtained with broadcast ephemerides.
