Abstract: Being a deformation measurement with high resolution, borehole tiltmeters should be installed far away from disturbance sources as far as possible. Rivers, lakes, large warehouses and railway are some of the main sources of disturbance affecting the tilt field due to mechanical loading and unloading on the surface. In this paper, the author proposed different models for each of these disturbances, in order to estimate the shortest "quiet" distance between a borehole tilt observatory site and the disturbance sources for certain threshold.

Key words: Borehole tilt observatory, Disturbance, least “quiet” distance