2007 Volume 56 Issue 9 Pages 839-845
High-resolution tilt meters have been applied to measure subtle underground tilt variations. As one of the application of high-resolution tilt meters system, the tilt variations recorded by the tilt meter can be used to monitor the distribution of underground volumetric deformation for CO2 injection. The signal recorded by the tilt meter is frequently affected by noises. In order to monitor the flow zone of injected CO2 using the tilt meters, it is important to consider eliminating the tilt variations due to noises such as earth tide, ground vibration, temperature variation, atmospherical pressure change, rainfall, and snowfall. In this paper, using the tilt data obtained from the observation field in Yubari, Hokkaido where high-resolution tilt meters are installed during CO2 injection test, we tried to estimate the tilt variations influenced by rainfall and snowfall. The tilt variations are theoretically determined by the elastic modulus of the surface soil in the field. First, we estimated the elastic modulus of the surface soil in the observation field using the load test and evaluated the tilt variations when removing snow using the estimated elastic modulus. Second, applying the tank model to precipitation data in the observation field, we estimated the tilt variations influenced by rainfall. The estimated tilt variations influenced by rainfall and removing snow are fit to tilt values observed in the field. Estimating tilt variations by rainfall and snow fall using the load test and the tank model is effective to evaluate the tilt variations influenced by the external factors.
