Natural time and 1/f "noise"
Abstract
Seismic electric signals have been found to obey the ubiquitous
1/
f
a
behavior [{\em Phys. Rev. E} {\bf 66}, 011902(2002)]. The newly introduced concept of natural time enables the study of the dynamic evolution of a complex system and identifies when the system enters the critical stage. On the basis of this concept, a simple model is proposed here which exhibits the
1/
f
a
behavior with
a
close to unity. Furthermore, we present recent data of electric signals, which when analyzed in the natural time domain are found to exhibit {\em critical} dynamics and hence can be classified as seismic electric signals.