P. Kapiris

Transmission of stress induced electric signals in dielectric media

The conditions under which pressure (stress) variations on solids, containing charged defects, can lead to the emission of transient electric signals, are discussed. The resulting electric field E varies as 1/d3 (where d denotes the distance from the emitting source), in the simple case when the surrounding medium is homogeneous and isotropic. We show that this behavior changes to 1/d when studying the electric field within a cylindrical channel of radius R and infinite length having conductivity appreciably larger than that of the host medium; this holds up to a certain (reduced) distance d/R, which increases versus the conductivity ratio. We also investigate the variation of the electric field, versus the distance, inside a layer of width w and infinite extent having conductivity appreciably larger than that of the host medium; we then find that the electric field decreases as 1/d2, in a wide range of distances up to a certain value of d/w, which is controlled by the conductivity ratio. In both conducti...

Signature of pending earthquake from electromagnetic anomalies

Two electromagnetic (EM) anomalies have been detected in the VLF frequency band before the Athens earthquake (EQ) (Mw=5.9, Sept. 7, 1999) with the following characteristics: (i) The first and second anomaly lasted for 12 and 17 hours respectively with a cessation of 12 hours; (ii) The second anomaly ceased at about 9 hours before the EQ; (iii) The larger anomaly, the second one, contains approximately 80% of the total EM energy received; (iv) No EM disturbance has been recorded in the VHF frequency band unlike with other cases, e.g., the Kozani Grevena and Egion-Eratini earthquakes. The fault modeling of the Athens EQ, based on information obtained by radar interferometry, predicts two faults. The main fault segment is responsible for 80% of the total energy released, while the secondary fault segment for the remaining 20%. Moreover, a recent seismic data analysis supports the hypothesis that a two-event solution for the Athens EQ, is more likely than a single event solution. In addition, the absence of surface rupture explains the absence of EM detection in the VHF frequency band. The present analysis reveals that the properties of the preseismic electromagnetic anomalies might be considered as signatures of a pending earthquake.

Numerical model of the selectivity effect and the ΔV/L criterion

Numerical solutions of Maxwell equations for a model earth with a reasonably conducting channel indicate that the electric field values are intensified within a certain region only (i.e., above the end of the channel), thus explaining the observed selectivity effect. In this region, the electric field may reach detectable values (5–10mV/km), while the magnetic field still remains low (10−2nT). The results are compatible with those obtained recently by analytical solutions (Varotsos et al. [1998]). Both the numerical and the analytical solutions lead to a natural explanation of the ΔV/L≈const criterion. This criterion, however, should not be applied over an area with strongly inhomogeneous electrical structure.

VHF-electromagnetic evidence of the underlying pre-seismic critical stage

Based on the study of pre-seismic very high frequency (VHF) and very low frequency (VLF) electromagnetic signals, we attempt to establish a set of necessary conditions referring to the underlying critical stage of the earthquake preparation process. This study combines concepts from spectral analysis associated with critical point hypothesis, results from laboratory experiments of rupture and seismological arguments. These conditions are fully satisfied in the case of the VLF-VHF pre-seismic signals associated with the Kozani-Grevena earthquake in Greece.

Prediction of the 6.6 Grevena-Kozani earthquake of May 13, 1995

Abstract Seismic Electric Signals (SES) were recorded by VAN-group on April 18–19, 1995, at Ioannina station; they resulted in an official prediction that was sent (two weeks before the earthquake occurrence) to the Greek authorities as well as to various International Institutes. The observation of these electrical variations was confirmed by Gruszow et al. (1996); however, they claim that these signals could be attributed to a (non determined) nearby artificial source with huge intensity (IL≈4 × 10 4 Am, for r ≈ 2 km. or 1.6 × 10 5 Am, for r ≈ 4 km). This claim is not valid, because, such an artificial source (cf. horizontal point current dipole) should have produced: (a) electrical field variations having amplitudes two orders of magnitude, larger than the observed ones; this is theoretically shown and experimentally verified and (b) magnetic field variations mainly on the horizontal field, while, in the present case, they have been recorded mainly on the vertical component. Furthermore, we show that the above SES obey the criteria, suggested by Varotsos and Lazaridou (1991), for discriminating SES from noise.

Distinguished seismological and electromagnetic features of the impending global failure: Did the 7/9/1999 M5.9 Athens earthquake come with a warning?

Clear VLF electromagnetic (EM) anomalies were detected prior to the Athens earthquake (EQ). We attempt to establish the hypothesis that these emissions were launched from the pre-focal area during micro-fracturing process. The spectral analysis in terms of fractal dynamics reveals that distinquished alterations in the associated scaling parameters emerge as the EQ is approached. These alterations suggests that the evolution of the Earth’s crust towards the “critical point” takes place not only in the seismological sense but also in the pre-fracture EM sense. VAN-signals and space-time TIR-signals were also detected prior to the Athens EQ. These anomalies, as well as the fault modeling of the Athens EQ obtained by interferometric combinations of ERS2 SAR images bring further support for the confidence in the reliability of our conclusions.