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1

Preseismic Earth's electric field anomalies recorded at Lesvos station, northeastern Aegean

Hadjicontis V., Mavromatou C., Eftaxias K.

Acta Geophysica Polonica

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2002

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Vol. 50, nr 2

151-158

EN

Significant electromagnetic preseismic activity has been recently recorded at the telemetric VAN station of Lesvos Island, northeast Aegean, Greece. This was followed, after a few weeks, by intense seismic activity with Ms 5.8, close to Psara island (38.5°N, 25.6°E). These field results are strongly correlated with laboratory experiments aiming at detection of electromagnetic signals before the fracture of rock samples.

2

The physical mechanism of seismic electric signals

Varotsos P., Hadjicontis V., Nowick A.

Acta Geophysica Polonica

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2001

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Vol. 49, nr 4

415-421

EN

Seismic Electric Signals are low frequency (< 0.1 Hz) transient electrical variations that precede earthquakes, with a lead-time ranging from several hours to a few weeks. In order to better analyze and interpret these signals, it is important to understand the physical mechanism that gives rise to them. The present paper is aimed at that objective. Specifically, we claim that the deformation-induced charge flow phenomenon, discovered more than 40 years ago, could provide the explanation for various aspects of these signals.

3

Anomalous piezoelectric effect: analysis of experimental data and numerical simulation

Teisseyre K., Hadjicontis V., Mavromatou C.

Acta Geophysica Polonica

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2001

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Vol. 49, nr 4

449-462

EN

Interpretation of laboratory experiments on anomalous piezoelectric effects found in samples of various non-piezoelectric rocks leads us to formulate the model of transient electric polarization and its relaxation. A change of the load results in polarization in the rock, the electric signal appears immediately at a given moment, and later we observe the signal relaxation as an exponential decrease in time. Assumption of double mechanism of relaxation or, for most cases, even triple mechanism: quick, slower and the slowest relaxation, is made to obtain a better agreement between simulation and the experiments. Other complications of the model seem to be useful in the search for adequate reconstruction of electric signal rise and decay. The following elements were assumed, and positively tested in many simulations: opposite components of polarization in case of serrate stimulus curve (load rate shaped like toothed curve), the large bay of the opposite polarization during release of the load (theoretically not expected in non-piezoelectric materials) and kind of the polarization saturation during the test with the repeating load history.

4

A note on the extent of the SES sensitive area around Lamia (LAM), Greece

Varotsos P., Eftaxias K., Hadjicontis V., Bogris N., Skordas E., Kapiris P., Lazaridou M.

Acta Geophysica Polonica

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1999

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Vol. 47, nr 4

435-444

5

On the extend of the ses sensitive area around ioannina. Additional evidence II.

Varotsos P., Borgis N., Eftaxias K., Hadjicontis V., Lazaridou M., Kefalas M.

Acta Geophysica Polonica

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1998

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Vol. 46, nr 4

411-413

EN

The SES activity at IOA on june21, 1998, was actually followed by aM5(ATH) = 5.6 earthquake. New SES activites were again recorded at IOA on August 14 - 17 and September21, 1998, and confirm ealier estimates on the extent of the sensitive area around Ioannina station.

6

Additional evidence on the extent of the SES sensitive area around ioannina

Varotsos P., Bogris N., Extaxias K., Hadjicontis V., Lazaridou M., Kefalas M.

Acta Geophysica Polonica

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1998

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Vol. 46, nr 3

273-275

EN

The SES activity recorded at IOA on June 21, 1998, confirms arlier estimates on the extent of the sensitive area around Ioannina station.