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1

Additional evidence on some relationship between seismic electric signals and earthquake source parameters

Varotsos P., Sarlis N., Skordas E., Tanaka H., Lazaridou M.

Acta Geophysica Polonica

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2005

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Vol. 53, nr 3

293-298

EN

We provide recent experimental evidence which further supports the inter-relation between the earthquake source parameters and the selectivity properties of Seismic Electric Signals. The cases of two major earthquakes with magnitudes larger than 6.0, that occurred in Greece during 2004-2005, are presented.

2

SES activity recorded at Keratea station on April, 2003

Varotsos P., Sarlis N., Skordas E., Lazaridou M.

Acta Geophysica Polonica

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2004

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Vol. 52, nr 1

45-48

EN

Two notes on the seismic electric signals recorded at the Keratea station, Greece, are presented. Both these signals as well as the subsequent seismic activ-ity have been analysed in the natural time domain. They have been finally fol-lowed by a 4.7 earthquake on June 13, 2003 with an epicenter at 38.6N, 23.7E (i.e., around 65 km north of Athens).

3

Four notes on SES activity at the Ioannina Observatory, Greece

Varotsos P., Sarlis N., Skordas E., Lazaridou M.

Acta Geophysica Polonica

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2003

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Vol. 51, nr 2

147-153

EN

Four notes are presented on the seismic electric signals recorded at the Ioannina Observatory, Greece and their relation to the seismicity of the area. The motes were issued between November 2, 2002 and January 12, 2003.

4

Note on an important SES activity at Ioannina station (IOA)

Varotsos P., Sarlis N., Skordas E., Lazaridou M.

Acta Geophysica Polonica

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2002

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Vol. 50, nr 3

355-359

5

Transmission of stress induced electric signals in dielectric media. Part II

Varotsos P., Sarlis N., Lazaridou M.

Acta Geophysica Polonica

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2000

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Vol. 48, nr 2

141-177

EN

In the previous paper the electric field Einside, inside a conductive path (and along its axis), having a conductivity s appreciably larger than that of the host medium, s', was studied in the static approximation, for the case of a current dipole source parallel to the path. Here, the same problem is studied but for a source perpendicular to the path. The following two types of paths we considered: (i) a cylindrical channel of radius R and infinite length, and (ii) a layer of width w and infinite extent. If D denotes the distance of the source from the path, and d the distance of the measuring site from the source, we find that the electric field Einside at remote sites (e.g., d/R or d/w of the order of 10(2)) varies as 1/D for the case of a source neighboring to the conductive cylinder, while it is almost independent of D (and w) for the case of a layer. In the case of the cylinder, the values of the ratio Einside/Ehost at (d/R)crit (see the previous paper); significantly exceed (e.g., by one order of magnitude for usual conductivity ratios between 200/1 and 4000/1, but for appreciably small values of D/R, e.g., D/R=2) the corresponding values when the dipole is parallel to the path. The general case, when the dipole source forms a certain angle with its neighboring highly conductive path terminating inside the host medium, is also investigated. The following four points emerge as far as the electric field Eoutside measured inside the more resistive medium but close to an edge is concerned. First, its direction is regulated from the angle between the emitting dipole and the direction of the (elongated) conductive path (as well as from the distance of the source). Second, its amplitude is usually larger than that of Ehost by a factor of around s/s', but there arc also some cases of over-amplification, i.e., the value of Eoutside/Ehost significantly exceeds the conductivity ratio s/s': such an over-amplification may even occur in cases of conductive paths that are not connected. Third, its amplitude versus the distance from the edge varies only slowly, i.e., [Eoutside] 1/r(t) where t is around (but smaller than) unity. Fourth, for a circularly polarized EM plane wave incident on the surf ace of a conductive half-space (containing a highly conductive path close to the interface), the direction of the electric field variations, measured on the surface but close to the end of the path, is generally different from the direction of Eoutside arising from a dipole source which forms a certain angle with its neighboring conductive path. Finally, the above points are applied to the case of the low frequency electric signals that are detected before earthquakes; this results in a natural explanation of the procedure that is followed to determine the parameters of an impending earthquake from the components of the precursory electric signal.

6

Comments on the predictions of large earthquakes issued by VAN during the last decade

Dologlou E., Lazaridou M.

Acta Geophysica Polonica

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1999

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Vol. 47, nr 1

59-75

EN

Uyeda in an intuitive study has recently shown that an investigation of the predictions issued for large earthquakes in Greece can give a convincing answer to the question whether or not VAN predictions are to be ascribed to chance. In this paper, we give clarifications concerning some misunderstanding on the VAN predictions (of large earthquakes) issued by VAN during the last decade.

7

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

8

Statistical evaluation of eqrthquake prediction results. Comments on the success rate and alarm rate. II

Varotsos P., Sarlis N., Lazaridou M.

Acta Geophysica Polonica

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1998

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Vol. 46, nr 3

261-271

EN

Following the procedure of Varotos et al. (1996) for an earthquake prediction method, that issues predictions whenthe expected megnitude Mpred (with a tolerance ?M0 exeeds a certain threshold, i.e., Mpred>mp, we show that: (1) The method also naturally predicts a fraction of the earthquakes (EQ) with magnitudes (MEQ) smaller than the target, i.e. mp - DMŁMEQ

9

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.

10

Note on the extension of the SES sensitive area at Ioannina station, Greece

Varotsos P., Eftaxias K., Lazaridou M., Bogris N., Makris J.

Acta Geophysica Polonica

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1998

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Vol. 46, nr 1

55-60

EN

A detailed experimentation shows that the SES sensitive area in loannina region extends to a zone (with width of a few kilometers and length of the order of 10 km) directed almost NW of Ioannina lake. The dimensions of the zone are compatible with recent theoretical estimations obtained from analytical and numerical solutions of Maxwell equations.

11

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.