Abstract
Characteristic tilt and strain changes are often observed at the time of rainf ails by horizontal pendulum tiltmeters and extensometers at the Yura station, Wakayama Prefecture. Large temporal changes have been found on the amount of tilts caused by rainfalls during the period of these 28 years. Remarkable correspondence of the temporal changes to secular ground tilts at Yura and to the occurrence of local shocks in this region suggests that the deformation of the tunnel caused by rainfalls reflects temporal changes in the crustal stress field through the behavior of underground water. In order to investigate such phenomena more precisely, response curves of ground tilts or strains should be estimated from the amount and pattern of rainfalls. A tank model has been applied to simulate the strain response to rainfalls observed at Yura. Preliminary results show that the strain response is successfully simulated by using a model with two tanks and taking the initial loss of rainfalls and the evapo-transpiration into consideration.
