Study in the natural time domain of the entropy of dichotomic geoelectrical and chaotic time series

The so-called seismo-electric signals (SES) have been considered as precursors of great earthquakes. To characterize possible SES activities, the Natural Time Domain (NTD) (Varotsos et al., 2001) was proposed as adequate methodology. In this work we analyze two geoelectric time series measured in a very seismically active area of South Pacific Mexican coast, and a chaotic time series obtained from the Liebovitch and Thot (LT) chaotic map. The two analyzed geoelectric signals display possible SES activities associated with the earhquakes occurred on October 24, 1993 (M6.6, epicenter at (16.54N, 98.98W)) and on September 14, 1995 (M7.4, epicenter at (16.31N, 98.88W)). Our monitoring station was located at (16.50N, 99.47W) close to Acapulco city and the experimental set-up was based on the VAN methodology. We found that the correlation degree of the SES geoelectric signals increases before the occurrence of the seismic events with power spectrum and entropy calculated in NTD in good agreement with analogous studies in the field of earthquake-related phenomena. Such SES activity, analysed in NTD, can be discriminated from the LT- chaotic map and from artificial noises. Varotsos P.A., Sarlis N.V., Skordas E.S., Practica of Athens Academy 76, (2001) 294 Liebovitch S.L. and Thot T.I., J. Theor. Biol., 148(1991), 243-267