Dielectric properties of Granodiorite partially saturated with water and its correlation to the detection of seismic electric signals

Transient electric signals emitted prior to earthquake occurrence are recorded at certain sites in the Earth's crust termed sensitive. These field observations enforce the laboratory investigation of the dielectric response of rocks forming these localities. The dielectric relaxation of granodiorite rock coming from such a sensitive locality (Keratea, Greece) reveals, through complex impedance spectroscopy, that the activation volume for relaxation of this rock is negative which so far has been reported only rarely. This result, however, supports a theoretical model on the pre-seismic electric signals and is likely to be correlated with the sensitivity of the site and hence with the selectivity

Negative activation volume for dielectric relaxation in hydrated rocks

Negative defect activation volumes are extremely rare in solids. Here, we report for the first time that this holds in a couple of hydrated rocks for dielectric relaxation by exploring the complex impedance spectra at various pressures and temperatures. The present findings mean that the relaxation time of the relevant relaxation mechanisms decreases upon increasing pressure, thus it may become too short at higher pressure and hence lead to the emission of transient electric signals before fracture. This may constitute the long-standing laboratory confirmation for the explanation of the generation of electric signals prior to an earthquake, as recently pointed out by Uyeda et al [Tectonophysics 470 (2009) 205-213]

Pressure dependence of the dielectric loss in semi-conducting polypyrrole aged at room temperature

The effect of physical aging of semi-conducting polypyrrole at ambient temperature for two years duration on the dielectric loss at various pressures is investigated. Changes of the dielectric loss spectra and the modification of the values of the activation volume for relaxation are interpreted through the division of chain clusters into smaller components and the reduction of the size of the conductive grains.Comment: Synthetic Metals (in print

Similarity of fluctuations in correlated systems: The case of seismicity

We report a similarity of fluctuations in equilibrium critical phenomena and non-equilibrium systems, which is based on the concept of natural time. The world-wide seismicity as well as that of San Andreas fault system and Japan are analyzed. An order parameter is chosen and its fluctuations relative to the standard deviation of the distribution are studied. We find that the scaled distributions fall on the same curve, which interestingly exhibits, over four orders of magnitude, features similar to those in several equilibrium critical phenomena (e.g., 2D Ising model) as well as in non-equilibrium systems (e.g., 3D turbulent flow).Comment: 5 pages, 9 figure

Effect of significant data loss on identifying electric signals that precede rupture by detrended fluctuation analysis in natural time

Electric field variations that appear before rupture have been recently studied by employing the detrended fluctuation analysis (DFA) as a scaling method to quantify long-range temporal correlations. These studies revealed that seismic electric signals (SES) activities exhibit a scale invariant feature with an exponent $\alpha_{DFA} \approx 1$ over all scales investigated (around five orders of magnitude). Here, we study what happens upon significant data loss, which is a question of primary practical importance, and show that the DFA applied to the natural time representation of the remaining data still reveals for SES activities an exponent close to 1.0, which markedly exceeds the exponent found in artificial (man-made) noises. This, in combination with natural time analysis, enables the identification of a SES activity with probability 75% even after a significant (70%) data loss. The probability increases to 90% or larger for 50% data loss.Comment: 12 Pages, 11 Figure

Natural entropy fluctuations discriminate similar looking electric signals emitted from systems of different dynamics

Complexity measures are introduced, that quantify the change of the natural entropy fluctuations at different length scales in time-series emitted from systems operating far from equilibrium. They identify impending sudden cardiac death (SD) by analyzing fifteen minutes electrocardiograms, and comparing to those of truly healthy humans (H). These measures seem to be complementary to the ones suggested recently [Phys. Rev. E {\bf 70}, 011106 (2004)] and altogether enable the classification of individuals into three categories: H, heart disease patients and SD. All the SD individuals, who exhibit critical dynamics, result in a common behavior.Comment: Published in Physical Review