Secular crustal deformation in central Japan, based on the wavelet analysis of GPS time-series data

We adopted the wavelet technique to analyze the GPS time-series data of daily co-ordinates from the continuous GPS network, GEONET, during a four-year period (1996-1999). In the present analysis we removed the data jumps associated with earthquakes and due to artificial errors using ARMA technique, and also removed seasonal variations and white noises using the wavelet technique to estimate the secular crustal deformation in central Japan. The secular displacement vectors obtained were used to calculate various crustal strain fields in the study area by means of the least squares prediction technique. The secular displacement field was different from that estimated from the raw GPS time-series data, and we would have overestimated the secular strain components without considering them. The main characteristic features of the secular strain fields were as follows: (1) there existed a compressive regime in the entire region; (2) there was a remarkable peak around Tokyo Bay in the maximum shear strain distribution; (3) along the Shinanogawa seismic zone there existed a distinguishing boundary zone in the several kinds of strain fields.