Denisse Pastén

Finite data-size scaling of clustering in earthquake networks

An earthquake network is known to be of the small-world type. The values of the network’s characteristics, however, depend not only on the cell size (i.e., the scale of coarse graining needed for constructing the network) but also on the size of a seismic data set. Here, discovery of a scaling law for the clustering coefficient in terms of the data size, which is referred to here as finite data-size scaling, is reported. Its universality is shown to be supported by the detailed analysis of the data taken from California, Japan and Iran. Effects of setting a threshold of magnitude are also discussed.

Characterization of the nontrivial and chaotic behavior that occurs in a simple city traffic model.

We explore in detail the nontrivial and chaotic behavior of the traffic model proposed by Toledo et al. [Phys. Rev. E 70, 016107 (2004)] due to the richness of behavior present in the model, in spite of the fact that it is a minimalistic representation of basic city traffic dynamics. The chaotic behavior, previously shown for a given lower bound in acceleration/brake ratio, is examined more carefully and the region in parameter space for which we observe this nontrivial behavior is found. This parameter region may be related to the high sensitivity of traffic flow that eventually leads to traffic jams. Approximate scaling laws are proposed.

Multifractal analysis of three large earthquakes in Chile: Antofagasta 1995, Valparaiso 1985, and Maule 2010

A multifractal analysis of seismicity of three large earthquakes in Chile is made: the Central Zone 1985 (MW = 8.0), Antofagasta 1995 (MW = 8.1), and Maule 2010 (MW = 8.8) earthquakes. The analysis shows that the fractal dimension spectrum Dq decreases with time before an earthquake. This fact suggests that the spatial distribution of seismic events could form a cluster before a main shock.

Experimental results on hard x-ray energy emitted by a low-energy plasma focus device: a radiographic image analysis

The PF-400J plasma focus device (400 J of energy) was studied in a similar way to a pulsed source of high-energy x-ray radiation. High-sensitivity fast-response commercial radiographic film and different metal filter array combinations were used to study the energy of the proper emitted x-ray. The effective energy of the hard x-ray radiation is studied and discussed in terms of its effective mean attenuation with the penetration distance on different metallic samples when the x-ray pulsed beam is supposed monoenergetic. These results were then used to assess the energetic properties of the pulsed radiation when different x-ray film–filter array combinations were irradiated between tens to almost 160 effective pulses of x-ray coming from the PF-400J device.

Time series analysis in earthquake complex networks

We introduce a new method of characterizing the seismic complex systems using a procedure of transformation from complex networks into time series. The undirected complex network is constructed from seismic hypocenters data. Network nodes are marked by their connectivity. The walk on the graph following the time of succeeding seismic events generates the connectivity time series which contains, both the space and time, features of seismic processes. This procedure was applied to four seismic data sets registered in Chile. It was shown that multifractality of constructed connectivity time series changes due to the particular geophysics characteristics of the seismic zones-it decreases with the occurrence of large earthquakes-and shows the spatiotemporal organization of these seismic systems.