Alejandro Ramirez-Rojas

Relationship between the Frequency Magnitude Distribution and the Visibility Graph in the Synthetic Seismicity Generated by a Simple Stick-Slip System with Asperities

By using the method of the visibility graph (VG) the synthetic seismicity generated by a simple stick–slip system with asperities is analysed. The stick–slip system mimics the interaction between tectonic plates, whose asperities are given by sandpapers of different granularity degrees. The VG properties of the seismic sequences have been put in relationship with the typical seismological parameter, the b-value of the Gutenberg-Richter law. Between the b-value of the synthetic seismicity and the slope of the least square line fitting the k-M plot (relationship between the magnitude M of each synthetic event and its connectivity degree k) a close linear relationship is found, also verified by real seismicity.

Non-extensivity analysis of seismicity within four subduction regions in Mexico

The non-extensivity approach based on the Tsallis entropy has been applied to seismicity that occurred from 1988 to 2010 along the Mexican South Pacific coast. We analyzed four different regions, characterized by different subduction patterns. Our results indicate a possible correlation between the non-extensive parameters and the seismicity pattern associated with the inclination angle of each subduction region.

Multifractal detrended fluctuation analysis of earthquake magnitude series of Mexican South Pacific Region

The multifractality of the earthquake magnitude series of seismicity occurred on the Mexican South Pacific Coast was investigated. The area is composed by five seismic regions that are characterized by different tectonic subduction features, due to the interactions between the La Rivera and Cocos plates with the North America plate. Among the five seismic regions, Jalisco is tectonically characterized by the existence of active spreading center (the East Pacific Rise). The multifractal analysis shows that all the five seismic regions are characterized by very close multifractal properties; however, Jalisco is featured by a higher persistence of the magnitude series.

The Complexity Measures Associated with the Fluctuations of the Entropy in Natural Time before the Deadly México M8.2 Earthquake on 7 September 2017

We analyse seismicity during the 6-year period 2012–2017 in the new time domain termed natural time in the Chiapas region where the M8.2 earthquake occurred, Mexico’s largest earthquake in more than a century, in order to study the complexity measures associated with fluctuations of entropy as well as with entropy change under time reversal. We find that almost three months before the M8.2 earthquake, i.e., on 14 June 2017, the complexity measure associated with the fluctuations of entropy change under time reversal shows an abrupt increase, which, however, does not hold for the complexity measure associated with the fluctuations of entropy in forward time. On the same date, the entropy change under time reversal has been previously found to exhibit a minimum [Physica A 506, 625–634 (2018)]; we thus find here that this minimum is also accompanied by increased fluctuations of the entropy change under time reversal. In addition, we find a simultaneous increase of the Tsallis entropic index q.

Investigating the time dynamics of photon sequences scattered by tracer particles immersed in a polymeric gel

By dynamic light scattering, we study the effects of spatial confinement of tracer colloidal particles immersed in polyacrylamide networks on the time dynamics of sequences of elapsed times of scattered photons. We vary the degree of particles spatial confinement by changing the concentration of crosslinker in solution, from 0 to 2% in monomer mass fraction, which allows us to change the elasticity of the polymer gel. By calculating the Allan factor of the point processes of scattered photons arrival times, we are able to characterize the statistical properties of the scattering process. For all the samples we find that: i) the statistics of the photon arrival times is not Poissonian but clusterized in a certain counting time interval; ii) the time dynamics of the photon sequences is fractal in an ample range of counting times, from ~10−3 to ~10−1 s, with scaling exponents ranging between ~1.7 and ~1.0; iii) the crosslinking density of the polymer network, and thus, the system elasticity is correlated with the value of the fractal exponent. The value of the fractal exponent decreases as the system elasticity, or tracers spatial confinement, increases.

NON-UNIFORM SCALING BEHAVIOR IN SELF-POTENTIAL EARTHQUAKE-RELATED SIGNALS

The scaling properties of the time dynamics of self-potential data (in the frequency range between 0 and 0.125Hz) observed in 1995 at Acapulco station in Mexico were investigated. On the basis of detrended fluctuation analysis (DFA), which is a powerful method to detect scaling in nonstationary time series, deviations from uniform power-law scaling were identified and quantified. Our results suggest that an evident non-uniform scaling behavior in self-potential data could be related to the occurrence on September 14, 1995 of the strongest earthquake. These first results could be useful in the framework of earthquake prediction studies.