Abstract
The observed earthquake scaling laws indicate the existence of phenomena closely associated with the proximity of the system to a critical point. Taking this view that earthquakes are critical phenomena (dynamic phase transitions), here we investigate whether in this case the Lifshitz–Slyozov–Wagner (LSW) theory for phase transitions showing that the characteristic size of the minority phase droplets grows with time as is applicable. To achieve this goal, we analyzed the Japanese seismic data in a new time domain termed natural time and find that an LSW behavior is actually obeyed by a precursory change of seismicity and in particular by the fluctuations of the entropy change of seismicity under time reversal before the Tohoku earthquake of magnitude 9.0 that occurred on 11 March 2011 in Japan. Furthermore, the Tsallis entropic index q is found to exhibit a precursory increase.
Highlights
Earthquakes exhibit complex correlations in time, space and magnitude and have been the object of a multitude of studies [1,2,3,4,5,6,7]
Recapitulating the aforementioned recent studies [12] related with the M8.2 earthquake that occurred in Mexico on 7 September 2017, which is Mexico’s largest earthquake in more than a century, we can say that upon employing natural time analysis we found that almost three months before its occurrence the following precursory behavior was identified: The entropy change under time reversal exhibits a minimum [12] along with increased fluctuations of the entropy change under time reversal as well as by a simultaneous increase of the Tsallis entropic index q [18]
Here we are going to answer the following question: If a super-giant earthquake is going to occur in a large area such as Japan, is it possible to identify a precursory behavior and estimate when the system approaches the critical point? This is answered in light of the fact that it is nowadays widely accepted, as for example stated by Holliday et al [9], that the observed scaling laws indicate the existence of phenomena closely associated with the proximity of the system to a critical point as already mentioned
Summary
Earthquakes exhibit complex correlations in time, space and magnitude and have been the object of a multitude of studies [1,2,3,4,5,6,7]. Recapitulating the aforementioned recent studies [12] related with the M8.2 earthquake that occurred in Mexico on 7 September 2017, which is Mexico’s largest earthquake in more than a century, we can say that upon employing natural time analysis we found that almost three months before its occurrence the following precursory behavior was identified: The entropy change under time reversal exhibits a minimum [12] along with increased fluctuations of the entropy change under time reversal as well as by a simultaneous increase of the Tsallis entropic index q [18] It is the main scope of this paper to investigate whether precursory behavior existed before the super-giant M9 Tohoku earthquake that occurred in Japan on 11 March 2011. Such a work providing an estimate of the region where the M9 Tohoku earthquake was going to occur had not been published before its occurrence in 2011. (Such an estimate of the epicentral area was published recently [35] as explained below in Section 5.) In view of the lack of such an information at that time, natural time analysis is made here for the seismicity that occurred in the whole Japanese area N46
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