arXiv subjects

G. Verveniotis

Publications and source records attributed to G. Verveniotis.

22 records · Page 2Linked to original sources

arXiv2008

Preseismic electric field "strange attractor" like precursor analysis applied on large (Ms > 5.5R) EQs, which occurred in Greece during December 1st, 2007 - April 30th, 2008

In order to investigate the capability of the preseismic electric field "strange attractor like" precursor as a time predictor of a large EQ within a short time window (short-term prediction), the specific methodology was applied on the Earth's electric field recorded during a rather long seismically active period (December 1st, 2007 - April 30th, 2008) of Greece. During this period of time a number (8) of large (Ms > 5.5R) earthquakes took place. The particular analysis is presented in detail for the following EQs: the Monemvasia EQ (January 6th 2008, Ms = 6.6R), the Methoni EQs (February 14th 2008 Ms = 6.7R, February 19th 2008 Ms = 5.6R, February 20th 2008 Ms = 6.5R, February 26th 2008 Ms = 5.7R), the Skyros EQ (March 19th 2008 Ms = 5.5R) and the Mid Southern Creta EQ (March 28th 2008 Ms = 5.6R). The obtained results from the analysis of the afore mentioned EQs, in conjunction to the ones obtained from an earlier presentation of the particular methodology (Thanassoulas et al. 2008a), suggest: an average time of initiation of the preseismic precursor of the order of (9) days before the EQ occurrence, a precursor average duration of the order of (7) days, while the elapsed time between the end of the precursor till the EQ occurrence time is, at average, only (2) days. These results suggest an objective and easy to apply method for the short-term EQ prediction, based on the registration of the Earth's electric field on ground surface.

physics.geo-ph↗

arXiv2008

On a preseismic electric field "strange attractor" like precursor observed short before large earthquakes

The Earth's electric field, recorded by two different and distant monitoring sites located in Greece, is analyzed in terms of monochromatic signals (T=24h). The analysis is based on the mapping procedures borrowed from the study of non-linear dynamic systems and chaos. The specific analysis applied on the electric field recorded for some weeks before the occurrence of 3 large EQs which occurred in Greece shows some very interesting results. Long before the EQ occurrence the phase map generated by the uncorrelated each other signals recorded by a pair of distant monitoring sites is characterized by pairs of hyperbolas of random azimuth asymptotes. Some days before the occurrence of the earthquake the recorded signals are strongly correlated and therefore the phase map is characterized by ellipses. A couple of days before the EQ occurrence the electric signals become again uncorrelated due to the fact that their generating mechanism (large scale piezoelectricity) approaches its final stage and therefore hyperbolas characterize again the phase map. When this stage is observed the pending EQ shortly (in terms of days) takes place. Three detailed examples from large Greek EQs are presented towards the validation of this mechanism.

physics.geo-ph↗

arXiv2008

Multidirectional analysis of the oscillating (T = 24 hours) Earth's electric field recorded on ground surface

The Earth's preseismic oscillating (T = 24h) electric field recorded for a short-time period of some days is analyzed in terms of its intensity vector azimuthal direction calculated at one monitoring site. The calculated azimuthal directions are compared to the concurrent seismicity observed for the same period of time. Examples are presented for proving the agreement between the electric field intensity vectors calculated azimuths and the corresponding ones referring to the EQs - monitoring site location. Finally, an example is presented on account of the use of this methodology upon three different monitoring sites for the utilization of the estimation of the epicentral area of a large future EQ at the Methoni, Greece seismogenic area.

physics.geo-ph↗

arXiv2008

Extracting preseismic electric signals from noisy Earth's electric field data recordings. The "noise injection" method

An entirely different approach is used for the extraction of preseismic electric signals from highly contaminated by noise data series. The basic element of this method is the "Dirac Delta Function". Noise is injected, instead of applying any known method of filtering, in the data series at different amplitude levels (p value) and the generated "family" of filtered data series is compared to different convergence criteria. In the case of preseismic electric signals identification the most appropriate (p) value is selected by testing the convergence of generated intersections of more than three "families" of filtered data which were generated from more than three monitoring sites. The "noise injection" method was tested against real data recorded long before two large earthquakes in Greece and one in Turkey.

physics.geo-ph↗