Institute of Geophysics of the CAS, v. v. i.


Earth tides

Earth tides monitoring and analysis

The Earth is affected by gravitational attraction of the Moon, the Sun and other Planets. Well known effects are the sea tides. However, even the solid Earth is affected and deformed by these external forces.

We study these effects from two different sides. The first one is to understand local dynamic conditions of the rock massif response to the tidal effects from the observed massif deformation. The second one is to correctly remove such tidal effects from observed geophysical and geological data in order to highlight geological signals related to tectonic processes. Such signals were identified in the groundwater level monitoring data before the first strong earthquake in August 2000 during the “Autumn 2000” earthquake swarm in West Bohemia.

We also performed a study of the relation between Earth tides amplitudes and earthquake occurrence in West Bohemia. Weak correlation between the two phenomena was proved.

Research team:

Lumír Skalský

Václav Polák 

Jan Mrlina 

Petr Skalský



* Vladimír Stejskal (IRSM ASCR, Prague)

* Alexej Lyubushin (SI RAS, Moscow)


Air-pressure effect was corrected in groundwater level observation data (well P1A) by two different correlation procedures. Sharp indications of earthquakes is obvious in the green line.

References cited:
* Barnet, I., Procházka, J. and Skalský, L. (1997): Do the Earth tides have an influence on short-term variations in radon concentration? - Radiation Protection Dosimetry, 69, No. 1, 51 - 60. Nuclear Technology Publishing.
* Fischer, T., Kalenda, P. and Skalsky, L. (2006): Weak tidal correlation of NW-Bohemia/Vogtland eartquake swarms. – Tectonophysics, 424, 259-269.
* Skalský, L., (1991). Calculation of theoretical values of the tidal strain components with respect to their practical use. Proceedings from seminary "Advances in gravimetry", December 10 - 14, 1990, Smolenice, pp. 179 - 184. Geophysical institute, Slovak academy of sciences, Bratislava.