Sensing of earthquake precursors with laser interferometer

Application of laser Michelson interferometers as the strainmeters for sensing of earthquake precursors is described. Earthquake precursors can appear as anomalous deformations (local irregular crustal movements and tilts, global slow periodical lithosphere oscillations) or anomalous changes of the Earth free oscillations in amplitude and frequency. The most perfect instrument with highest sensitivity to the crustal movements is the laser interferometer-strainmeter. The precursoral relative crustal movements have the order 10-6- 10-7 for irregular local strains and 2-3 orders less for slow global seismic oscillations. Laser interferometer sensitivity to the crustal movements is approved to reach about 10-12 and it is obviously enough for detection of any type of precursoral strains. Some results of two seismic stations equipped by the long-base laser interferometer-strainmeters and built in Russia, at the North Caucasus (Baksan canyon) and in the Ukraine, near the Black Sea (the Crimea peninsula) are analyzed. These stations make continuous monitoring to registrate the changes of crustal strains, investigate the total spectrum of the Earth free oscillations and dynamics of lithosphere slow deformations. The sensitivity of the instruments is so high that they registrate the earthquakes all over the world, and recent results are presented in this paper. There are some good approvals that the deformation precursors sensing is the most perspective way for the earthquake prediction, and the long-base laser interferometers-strainmeters demonstrate high possibilities in this application. Perspectives of development of the new laser interferometer-strainmeters based on Russia high optical technologies and unique design are discussed.