Deformation and acoustic precursors of earthquakes

Influence of a single lightning discharge on the intensity of an air electric field and acoustic emission of near-surface rocks

“…It determines the time of atmosphere relaxation near ground surface. According During lightning, a charge of 20-30 coulombs takes place with every lightning stroke (Feynman et al, 1964). Recovery occurs according to the same law as capacitor charge recovery.…”

“…Recovery occurs according to the same law as capacitor charge recovery. Here one may observe a sudden field fall followed by exponential return to its initial value with characteristic time constant of the order of 5 sec changing from time to time (Feynman et al, 1964). When studying ground-cloud discharges, the form of charge recovery is commonly calculated by the formula suggested by Kazemir (Chalmers, 1967):…”

“…The analyzed value is a summary for every 4 s acoustic pressure P s at every frequency channel. The performed investigations stated that, under the influence of deformations of the order ∼10 −7 (Dolgikh et al, 2007), an increase of emission activity is observed in the frequency range of first kilohertz which coincides with source scales of 10 −1 -1 m . This effect is the most vividly observed during strong earthquake preparation, 1-3 days before an event .…”

Features of the Earth surface deformations in the Kamchatka peninsula and their relation to geoacoustic emission

“…Hardness of landscapes, mountain slopes, glaciers, snow covers and large technical constructions are associated with mesoscale deformation processes. An increase in regional mesoscale deformations is observed at the final stage of earthquake preparation (Agnew and Wyatt, 2003;Berardino et al, 2002;Dolgikh et al, 2007;Sasorova et al, 2008). As a result, local effects of earthquake precursors of different natures appear, including those in acoustic signals of the sound range (Dolgikh et al, 2007;Gregori et al, 2005Gregori et al, , 2010Kuptsov, 2005;Levin et al, 2010;Morgunov et al, 1991;Paparo et al, 2002;Sasorova et al, 2008).…”

Electromagnetic and acoustic radiations before Kamchatka earthquake

“…The sensitivity of the hydrophone together with the pre-amplifier is the first hundreds of mV/Pa. The results of investigation of the acoustic emission in Kamchatka showed that acoustic radiation increase in the high-frequency range from hundreds of Hz to the first tens of kHz is determined by the intensification of rock deformations in the observation area including those associated with earthquake preparation [8]. Thus, high-frequency acoustic emission can be applied as a sensitive indicator of intensification of the deformation processes preceding seismic events [8,9].…”