Crustal movement imaging by D-InSAR, reflector array, dense GPS, leveling and gravity changes in the plate convergent zone, at the Tokai region, central Japan

In order to obtain more precise and quantitative crustal deformations, we combine the results of spaceborne differential interferometric synthetic aperture radar (D-InSAR), with the dense distribution of continuous Global Positioning System (GPS) observations, precise gravity measurements, and leveling surveys in the Tokai region, where dense and continuous geophysical and geochemical monitoring has been carried out due to the expected huge interplate earthquake. Seasonal uplift-subsidence motions of 2 to 6 cm are obtained from winter to the beginning of summer for both 1995 and 1997, that might be concordant with the leveling survey, although the atmospheric effects should play an important role for these conclusions. At the Sagara corner reflector, we have experimentally sifted the surface of the reflector and obtained fairly reasonable results, although the discrepancy of about 1.5 cm (along the line of sight) between theoretical estimate could be attributed to the unexpected contamination of noise from the surroundings and/or analytical processes.