Crustal strain field in central japan, based on the wavelet analyzed GPS time-series data

In order to estimate the secular crustal deformation in central Japan, we adopted the wavelet technique to find and remove the data discontinuities associated with earthquakes and artificial errors, and also remove seasonal variations and white noises in the GPS time series data of daily co-ordinates obtained from the continuous GPS network, GEONET of GSI. The strain components were computed based on least-squares prediction method by using improved time series data.The motion velocities of GPS sites at uniform 7 km × 7 km grids were interpolated by adopting the empirical covariance function and then differentiated with respect to space to estimate strain rates.The estimated strain field shows that there existed a compressive regime in the entire region. Higher maximum shear strain rates of about 0.2 microstrain/a are shown in and around the Izu and Boso peninsulas, and Tokyo Bay. Relatively high maximum shear strain rates are also shown in the southern Tohoku district and another notable area along the coast of the Japan Sea,which nearly corresponds to the Shinanogawa seismic zone.