A Nonextensive Statistical Physics Analysis of the 1995 Kobe, Japan Earthquake

This paper presents an analysis of the distribution of earthquake magnitudes for the period 1990–1998 in a broad area surrounding the epicenter of the 1995 Kobe earthquake. The frequency–magnitude distribution analysis is performed in a nonextensive statistical physics context. The nonextensive parameter qM, which is related to the frequency-magnitude distribution, reflects the existence of long-range correlations and is used as an index of the physical state of the studied area. Examination of the possible variations of qM values is performed during the period 1990–1998. A significant increase of qM occurs some months before the strong earthquake on April 9, 1994 indicating the start of a preparation phase prior to the Kobe earthquake. It should be noted that this increase coincides with the occurrence of six seismic events. Each of these events had a magnitude M = 4.1. The evolution of seismicity along with the increase of qM indicate the system’s transition away from equilibrium and its preparation for energy release. It seems that the variations of qM values reflect rather well the physical evolution towards the 1995 Kobe earthquake.