Vol.42-2 ABSTRACT2

Abstract

The nationwide permanent GPS array has been operated by the Geodetic Department since October 1,1994. The total system is named GRAPES(GPS Regional Array for PrEcise Surveying / Physical Earth Science). This network is deigned both for crustal deformation monitoring and to serve as a highly precise geodetic network in the GPS age. Most of the processing carried out automatically. This network has precisely monitored crustal deformation within several millimeters horizontally and several centimeters vertically.
    Since GSI had started the operation of this network, three major earthquakes occurred in and around Japan: the Hokkaido-Toho-Oki Earthquake on October 3,1994, the Sanriku-Haruka-OkiEarthquake on December 28,1994, and, the Hyogoken-Nanbu Earthquake on January 17,1995. GRAPES detected coseismic and postseismic crustal deformation caused by these earthquakes.
    By March 1996, this network will be combined with the COSMOS-G2 network in the Kanto Tokai area and 400 new stations will be added. The new dense nationwide GPS array will bring us more precise information not only of crustal deformation but also of other geophysical phenomena such as ionospheric disturbances and water vapor distribution. Accumulation of the data will produce a seismic hazard map. Moreover, the new network will serve as an active controlling system in Japan by GPS