Static vertical pendulums have been installed in mines and caves in Central Europe since 2007. The two dimensional optical measurement of tilt of rock mass and continuous full digital on-line evaluation of results makes possible to detect small tilt of the surroundings with resolution of tens of nanoradians or deformation of the surroundings in the horizontal plane with resolution of hundreds nanometers. The two years experience of measurement shows that it is possible to find the main direction of stress in the surroundings of the pendulum and its development in time. The noise level and anomalous deformation development shows the value of relative stress in the surroundings of the pendulum. The correlation of deformation between distant stations shows existence of stress variations that they are not of local origin. The stress field has wider than regional character and effects of very far origin can be observed. The great changes in stress orientation and in stress state were observed before the biggest earthquakes on the Eurasian lithosphere plate.
The current main task of seismology seems to be the prediction of earthquakes. Although the modern science uses many apparatus based on various principles, and it manages many sophisticated mathematical procedures, there is not generally accepted method how to predict the earthquake deterministically i.e. to assess the place, time window and magnitude of future earthquake. It can be seen ex-post that many of main shocks could be predicted and many of apparatuses or methods showed the detectable anomalies. One of the most important conclusions of the ISESEP 09 International Conference On Earthquake Prediction in Beijing says that for immediate prediction it is necessary to measure stress in rocks continuously using direct or indirect methods (Crampin & Gao 2009, Shi et al. 2009).