This paper addresses the capabilities of quartz tidal tiltmeters and different methods for their calibration, describing measurements of modern deformations and tidal and anthropogenic motions. Periodic thermal and anthropogenic variations in ground-based pedestal tilts (depth of 0-5 m) are estimated. Measurements in the vicinity of the water reservoir of the Irkutsk hydroelectric power station (HPS) showed that pedestal tilt angles reach 20-40 arcsec as a result of deformation of the ground surface due to changes in the reservoir load (water level variation 3-4 m). In the area of the Ust-Balykskii oil and gas field (Western Siberia), the annual tilt variations range from 8 to 90 arcsec. These variations, as well as short-term tilt changes up to 1 arcsec, are due to the oil and gas production operations, which cause buildings to sway in the city of Nefteyugansk. Tilt measurements were performed in deep adits of the Talaya seismic station (Lake Baikal Region, Russia) and the Walferdange observatory (Luxembourg). Based on these measurements, tidal deformations of the Earth, long-term variations in tilts, and coseismic deformations can be estimated. Based on tilt monitoring data at the Talaya seismic station from 1985 to 2015, tidal parameters were estimated and compared with models of the Earth's tidal deformations to recognize some particularities (phase shift 9°) related to structural specificities of the region. The long-term tilt measurement data were analyzed using elastic and viscoelastic models of the Earth's crust. It was found that an efficient estimate of viscosity in a deep-fault zone is 1019 Pa.s and that of stress variation in the Earth's crust is 0.5 MPa. These effective estimates can be used in modeling tectonic, anthropogenic, coseismic, and post-seismic processes.
