Groundwater-induced vertical movements observed in Tsukuba, Japan

Abstract

The anomalous vertical movements observed in Tsukuba and their relevance to groundwater level changes are investigated. First, we investigated the vertical coordinate time series of an IGS station TSKB w.r.t. a nearby stable site and found that the time series has a strong correlation with the groundwater level changes of the deep wells. Next, we investigated those of the GPS antenna attached at the tip of the antenna of Tsukuba VLBI station w.r.t. TSKB. We found that the time series is decomposed into components that have 1) high correlation with the groundwater level changes of the shallow wells, and 2) high correlation with the air-temperature. Poroelastic movements of aquifers due to groundwater level changes and thermal expansion of the VLBI antenna are likely for the mechanisms of these high correlations. Copyright 2004 by the American Geophysical Union.