Abstract
Continuous geoacoustic emission (GAE) measurements were acquired using a three-component geophone placed in a borehole at a depth of near 1000 m at Petropavlovsk-Kamchatsky starting in August 2000. Using geophones consisting of magneto-elastic crystal ferromagnetic sensors, and installed at such a depth allows measurement of natural geoacoustic background with signal amplitude less than 1×10 -4 m/s 3 in frequency band from 3 to 1500 Hz. According to the data from a 4-year survey period the characteristics of diurnal geoacoustic variations change before every earthquake with MLH≥ 5.0 that occurs at a distance of less than 300 km from the observation point or before each earthquake with MLH≥5.5 occurring at distance R≤550 km from the observation point. The changes in GAE regime correlate with the strongest earthquakes that occurred during survey period. Measurements of the natural electromagnetic field of the Earth were carried out simultaneously with the help of an underground electric antenna. The behavior of GAE in aseismic periods appears to be related to the effect of diurnal variations of the natural electromagnetic field.
Highlights
The concepts of cracking within heterogeneous media are the fundamental to modern models of earthquake preparation and source site formation
During primary data analysis we focused on manifestations of characteristic diurnal variations of averaged geoacoustic emission (GAE) levels
Characteristic variations constitute diurnal geoacoustic emission distributions (DGAED) of 24 hours periodicity which usually emerge in aseismic periods (Gavrilov et al, 2006)
Summary
The concepts of cracking within heterogeneous media are the fundamental to modern models of earthquake preparation and source site formation. Mailing address: Dr Leonid Bogomolov, Institute of Marine Geology and Geophysics of the Russian Academy of Science, Nauki str., 1 B, 693022, Yuzhno-Sakhalinsk, Russia tribute to validation and/or improvement of such models. This involves the results of laboratory-scale experiments on rock specimens to simulate tectonic straining processes, and geoacoustic emission (GAE) surveys (seismoacoustics, by other term (Belyakov et al, 1996)) aimed to study natural acoustic emission of embedded rocks. The measurements were carried out with the help of three-component MAG-3S geophone designed at Earth Physics Institute of the Russian Academy of Sciences on the basis of magneto-elastic sensor (Belyakov, 2000). The output signal of such sensor is proportional to the third derivative of the ground displacement, and the gain slope of MAG-3S geophone is equal to 60 Db
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