Variations in geoacoustic emissions in a deep borehole and its correlation with seismicity

V. Gavrilov, L. Bogomolov, Y. Morozova, A. Storcheus

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/s3 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.

Keywords


geoacoustic emission;deep borehole, diurnal variation;earthquake occurrence;natural electric field

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References


DOI: https://doi.org/10.4401/ag-3013
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Published by INGV, Istituto Nazionale di Geofisica e Vulcanologia - ISSN: 2037-416X