Effect of Groundwater on Gravity Observation at Kyoto
Effect of groundwater variations on gravity observation was examined by employing gravity data obtained from two superconducting gravity meters at Kyoto, as well as data of groundwater level and rainfall during the period from February 1992 to July 1996. Gravity changes of several μ gals were observed according to groundwater level changes of 2 m. The gravity changes are in proportion to the change of the groundwater level. The admittance was determined to be 3.56 μ gal/m and the gravity changes followed the change of the groundwater level with a lag of 1.6 day. The gravity changes due to groundwater variations can be calculated in the order of 1 μ gal by employing data of groundwater level obtained at a well. Although change of groundwater level can be estimated using rainfall data with the precision of a few tenths meter, response function of groundwater to rainfall should be revised when drainage condition is changed due to construction works near the station.
KeywordsGravel Cross Correlation Geophysics
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