Groundwater-induced vertical movements in Tsukuba revisited: installation of a new GPS station

Abstract

A new continuous GPS station, 06S061, was installed in Tsukuba, Japan, which is directly anchored to the soil at a depth of 190 m, so that it is less affected by seasonal poroelastic deformations of aquifers induced by groundwater extraction for irrigation. A comparison of GPS-derived vertical movements of surrounding GPS stations relative to 06S061 with the independent observations revealed that 06S061 has an observation quality comparable to a standard GPS station in terms of coordinate repeatability. The poroelastic deformations of aquifers below 190 m recorded at 06S061 were estimated to have peak-to-peak values of about 1 cm, which is half of the total poroelastic deformations of aquifers observed at surrounding GPS stations.

Time Variations of the Vertical Component in Some of Japanese GEONET GNSS Sites

“…Moreover, Geospatial Information Authority of Japan (GSI) in Heki (2001) adopted a specific processing that lead to erroneous vertical annual displacements. Although Tsukuba GSI Campus is showing significant annual variations by the nearby groundwater pumping for agricultural usage (Tobita et al 2004;Munekane et al 2004Munekane et al , 2010, the coordinates of Tsukuba IGS/GEONET site were fixed to ITRF96 (Boucher et al 1998) and the coordinate solution of each GEONET network site then derived by applying the backbone/cluster approach (Miyazaki et al 1997;Hatanaka et al 2003;Nakagawa et al 2009). Thus, Heki (2001) shows time series of vertical coordinate solutions at Naruko and Shizukuishi GEONET sites, but most of the annual variations at those sites are fake motions brought by the erroneous analysis strategy of F1 solution.…”