Earthquake Precursors: Stratification and Detection by Laser Strainmeter System

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One of the conventional models of earthquake preparations is: dilatance-diffusion model is being confirmed
by a lot of bay-like precursors frequently detected everywhere before the most powerful events. Distribution
of earthquake precursors from probably the inner core to the upper ionosphere gives rise to their spatial and
temporal interference. Thereupon the stratigraphy of earthquake precursors can be considered as a particular
display of these unusual geophysical phenomena. The quantitative correlation of processes in the lithosphere
and in adjacent geospheres has become possible in the last few decades when high quality laser strainmeters
– the most precise tools for earth surface observations have been manufactured. Here we summarize the ex-
perience in laser geophysical studies of short-term earthquake precursors over the past 30 years since our first
tangible results at the end of 1970th. Spaced laser instruments were installed in a non-seismic area (Moscow
Region) and in seismically active (Pamirs and Tien Shan) regions. The stratification of detected precursors are
classified as follows:
(a) wide band variations of a diurnal tension velocity from tens of hours up to a few days before an earthquake;
(b) deviations of strains with typical time of tens of minutes, amplitude dL/L = 10(-9), from a regular course;
(c) frequency of the appearance of the irregular course deviations, local microseism and sporadic occurrences ;
(d) acoustic precursors (the coherent micro-oscillations at industrial frequencies Fi = 50/i Hz, i = 1, 2, ..., that
accompany the strongest earthquakes with probability over 0.9), seismic and acoustic calms;
(e) strain-baric traveling anomalies (bay- and wave-like disturbances of the atmospheric pressure, strains of the
earth surface and underground water level variations) with velocity of travel 30-60 km/h;
(f) conversion of seismic wave-field energy and electromagnetic phenomena, lithosphere and ionosphere distur-
bances.
The pre-seismic and co-seismic events for the regional M=4 and remote M=7-8 earthquakes were found. The
obtained results can be applied to develop the technology for early warning of seismic hazard.