Spectrum of the seismic-electromagnetic and acoustic waves caused by seismic and volcano activity

Abstract

Part of Special Issue "Precursory phenomena, seismic hazard evaluation and seismo-tectonic electromagnetic effects" Abstract.Modeling of the spectrum of the seismoelectromagnetic and acoustic waves, caused by seismic and volcanic activity, has been done. This spectrum includes the Electromagnetic Emission (EME, due to fracturing piezoelectrics in rocks) and the Acoustic Emission (AE, caused by the excitation and the nonlinear passage of acoustic waves through the Earth's crust, the atmosphere, and the ionosphere). The investigated mechanism of the EME uses the model of fracturing and the crack motion. For its analysis, we consider a piezoelectric crystal under mechanical stresses, which cause the uniform crack motion, and, consequently, in the vicinity of the moving crack also cause non-stationary polarization currents. A possible spectrum of EME has been estimated. The underground fractures produce Very Low (VLF) and Extremely Low Frequency (ELF) acoustic waves, while the acoustic waves at higher frequencies present high losses and, on the Earth's surface, they are quite small and are not registered. The VLF acoustic wave is subject to nonlinearity under passage through the lithosphere that leads to the generation of higher harmonics and also frequency downconversion, namely, increasing the ELF acoustic component on the Earth's surface. In turn, a nonlinear propagation of ELF acoustic wave in the atmosphere and the ionosphere leads to emerging the ultra low frequency (ULF) acoustogravity waves in the ionosphere and possible local excitation of plasma waves.

Response of the ionosphere to the seismic trigerred acoustic waves: electron density and electromagnetic fluctuations

“…6a). It has been recently shown that only the AWs and AGWs in ULF frequency range (< 0.1 s −1 ) can reach to the F region heights (Koshevaya et al 2005). Thus δ W is expected to vary considerably with frequency in the ionosphere and the spectral features presented above may be modified once this aspect is taken into account.…”

“…These observations indicate the existence of energy flow mechanisms from the lithosphere to the ionosphere. The coupling through AGWs is found to be quite effective (Lognonné et al 1998; Koshevaya et al 2005) due to their excitation by the displacements of the terrestrial surface and their large amplitudes at ionospheric heights (Ahmadov & Kunitsyn 2004). Lognonné et al (1998) have shown that a fraction of about 10 −6 of the seismic energy is injected in the atmosphere for frequency larger than 5 mHz via this channel.…”

TEC variations over the Mediterranean during the seismic activity period of the last quarter of 2005 in the area of Greece

“…A lot of work has been done by a great number of researchers on the characteristics of ionospheric variations (wave-length, attenuation, velocity and way of propagation (Afraimovich et al, 2002)) according to their nature as well as on the theoretical explanation Rapoport et al, 2004a, b;Koshevaya et al, 2005). Nevertheless in order that TEC variations over a particular site are used as earthquake precursory diagnostic a concrete sense of the interrelation of TEC variations over different sites as well as their respond to the geomagnetic field variations would be of great interest.…”

Autonomous Instrumentation for Measuring Electromagnetic Radiation from Rocks in Mine Conditions—A Functional Analysis

“…It is worth mentioning that similar phenomena are also observed in plastic materials such as epoxy resin [43]. The equation relating the electric field strength E to the parameters of the micro-crack formed takes the form [46]:…”