Comments on the entropy of seismic electric signals under time reversal

TL;DR

This paper analyzes the entropy of seismic electric signals in natural time, confirming previous findings and demonstrating that entropy measures can distinguish seismic signals from noise and help determine their scaling properties.

Contribution

It provides new data confirming entropy behavior in seismic signals and introduces a scale-dependent fluctuation analysis for signal discrimination and scaling exponent estimation.

Findings

Entropy in natural time is lower than in uniform distribution.

Entropy under time reversal helps differentiate seismic signals from noise.

Scale dependence of fluctuations aids in identifying critical seismic dynamics.

Abstract

We present recent data of electric signals detected at the Earth's surface, which confirm the earlier finding [Phys. Rev. E 73, 031114 (2006)] that the value of the entropy in natural time as well as its value under time reversal are smaller than that of the entropy of a ``uniform'' distribution. Furthermore, we show that the scale dependence of the fluctuations of the natural time itself under time reversal provides a useful tool for the discrimination of seismic electric signals (critical dynamics) from noises emitted from manmade sources as well as for the determination of the scaling exponent.