Volume 65, Number 4, February 2004
|Page(s)||581 - 586|
|Section||Interdisciplinary physics and related areas of science and technology|
|Published online||01 February 2004|
Scale-free network of earthquakes
Institute of Physics, University of Tsukuba - Ibaraki 305-8571, Japan
2 College of Science and Technology, Nihon University - Chiba 274-8501, Japan
Accepted: 2 December 2003
The district of Southern California and Japan are divided into small cubic cells, each of which is regarded as a vertex of a graph if earthquakes occur therein. Two successive earthquakes define an edge or a loop, which may replace the complex fault-fault interaction. In this way, the seismic data are mapped to a random graph. It is discovered that an evolving random graph associated with earthquakes behaves as a scale-free network of the Barabási-Albert type. The distributions of connectivities in the graphs thus constructed are found to decay as a power law, showing a novel feature of earthquake as a complex critical phenomenon. This result can be interpreted in view of the facts that the frequency of earthquakes with large values of moment also decays as a power law (the Gutenberg-Richter law) and aftershocks associated with a mainshock tend to return to the locus of the mainshock, contributing to the large degree of connectivity of the vertex of the mainshock. Thus, a mainshock plays the role of a “hub”. It is also found that the exponent of the distribution of connectivities is characteristic for the plate under investigation.
PACS: 89.75.Da – Systems obeying scaling laws / 05.65.+b – Self-organized systems / 91.30.-f – Seismology
© EDP Sciences, 2004
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