Abstract
It has been shown that some dynamic features hidden in the time series of complex systems can be unveiled if we analyze them in a time domain termed natural time. In this analysis, we can identify when a system approaches a critical point (dynamic phase transition). Here, based on natural time analysis, which enables the introduction of an order parameter for seismicity, we discuss a procedure through which we could achieve the identification of the occurrence time of the M8.2 earthquake that occurred on 7 September 2017 in Mexico in Chiapas region, which is the largest magnitude event recorded in Mexico in more than a century. In particular, we first investigated the order parameter fluctuations of seismicity in the entire Mexico and found that, during an almost 30-year period, i.e., from 1 January 1988 until the M8.2 earthquake occurrence, they were minimized around 27 July 2017. From this date, we started computing the variance of seismicity in Chiapas region and found that it approached the critical value 0.070 on 6 September 2017, almost one day before this M8.2 earthquake occurrence.
Highlights
In the beginning of the 2000s, a new procedure for the study of complex time series, termed natural time analysis, was proposed [1,2,3,4]
As for the candidate area for the impending mainshock, Seismic Electric Signals (SES) data have not yet been reported, we considered the Chiapas region as mentioned in the Introduction for the reasons explained in our previous paper [38], where we used the results of the analysis of seismicity in the six areas of Mexico depicted in Figure 1a in natural time by Ramírez-Rojas and Flores-Márquez [39], which led to the identification of the properties of their probability density functions of the order parameter of seismicity pointing to an impending major EQ occurrence
It is worth noting that, by applying Detrended Fluctuation Analysis (DFA) [64,65,66,67,68,69,70,71,72], which is a method that has been developed to address the problem of accurately quantifying long range correlations in non-stationary fluctuating signals to the earthquake magnitude time series, we found that the minimum β min of the fluctuations of the order parameter of seismicity was observed during a period in which long range correlations prevailed since the corresponding DFA exponent a was larger than 0.5, in a similar fashion with what happened before the aforementioned Tohoku EQ
Summary
In the beginning of the 2000s, a new procedure for the study of complex time series, termed natural time analysis, was proposed [1,2,3,4]. Indicate the existence of phenomena closely associated with the proximity of the system to a critical point [1,5,18,19]. Following this view that earthquakes are critical phenomena, we face the difficulty to identify an order parameter, which is a parameter by means of which we can determine when the system approaches the critical point. The order parameter of a system in the critical
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