Application of laser interferometers-strainmeters for registration of geophysical processes in the acoustic frequency range

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Currently, laser interferometer measurement systems are the most accurate means employed for the registra-
tion of geodynamic, seismic and other geophysical deformation processes. In this report we describe the use of
laser interferometers-strainmeters for registration of geophysical processes in the acoustic range of frequencies.
Mobile and portable laser interferometers-strainmeters are used for measurements. In these devices we apply
three-mirror interferometer, which simplifies the installation and configuration in the field observation. The
laser radiation through a beam-splitting plate and electro-optical modulator is sent to the measuring arm. Part
of the laser radiation reflected from the beam-splitting plate, arrives at the photo-detector, which allocates the
electrical interference signal. The registration system of heterodyne type, which is resistant to the turbulent
distortions of the wave beam and which allows to measure in the open atmosphere, is used for a signal recording
in the frequency range 10(-5)-10(3) Hz. The comparison of data, obtained from the strainmeter and acoustic
sensors installed in the energy active zone, is performed. Observations were carried out on the IRE underground
beam waveguide (Moscow region), at the POI and IKIR FEBRAS Stations (Far East and Kamchatka region).
Research and development is aimed at creating technology for early detection of dangerous geodynamic pro-
cesses - earthquakes, landslides, tsunami waves. The produced version of laser strainmeters can be effective in
solving various problems: geological, geophysical and environmental services, construction, engineering infras-
tructure, etc. With their help, estimations of background processes in natural conditions may be carried out,
including industrial and construction facilities, and underground mine workings, researching expeditions and
field observation points. Further development of this work in IRE is planned to perform in close cooperation
with IKIR FEB RAS and other organizations.