Abstract
Collocative measurements by an absolute gravimeter have been carried out at Kashima Space Research Center, Communications Research Laboratory, one of the VLBI IRIS-P Networks, from January 18 to 23, 1988. The observation site is located near a manu facturing district and the ground vibrations caused by human activities such as traffic noise extremely affected the measurements . The maximum acceleration due to the traffic amounted to more than 2X10-4 ms-2 (20 mGal). The effects of the vibrations caused by the operation of the 26 m diameter antenna, on the other hand, were relatively small compared to the large traffic noise, so we could not detect them at the point about 30 m distant from the antenna. The uncertainty in the results from 194 drops is about 3X10-7 ms-2 (30μGal), which is almost ten times larger than that obtained at Esashi. The main cause of the error can be considered as the traffic vibrations and we can correct their effects with the accuracy better than one percent.
