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This paper reports results of mathematical modeling applied to the stress and strain in epicentral zones before and after the large earthquakes that occurred on June 22, 2002 in the Qazvin Province, northwestern Iran (Mw = 6.4) and the Gujarat, India earthquake of January 26, 2001 (M = 6.9). The modeling relied on a method for calculating stress and strain in a blocky elastic isotropic heterogeneous medium disturbed by a set of faults that are due to an external tectonic stress field. The boundary conditions were specified based on geological and seismological data. It has been shown that the epicenters of large crustal earthquakes occur in zones of high stress concentration at the ends of tectonic faults. Rupture occurs when the relationship between acting tectonic stresses satisfies the requirement σyy/σxx >3, thus connecting zones of high stress. The evolution of the aftershock process is controlled by the stress drop caused by a new rupture, while the resulting aftershock clusters are in spatial correlation with the stress drop zone. The new rupture propagates in the direction of dominant tectonic fault orientation in the region. We show a relationship to exist between rupture length and the possible retrospectively predicted location and magnitude of the earthquake depending on the elastic energy buildup and its possible release under specified structural tectonic conditions. [ABSTRACT FROM AUTHOR]

The paper presents the results of modeling the stress–strain state of the epicentral zone of the strong crustal Hanshin–Awaji earthquake, which occurred in the area of Kobe (Japan) on January 17, 1995, with a magnitude M of 6.9. In this work the author's method for modelling and analyzing the stress–strain state of the epicentral zones of crustal earthquakes was used. The geological, tectonic, and seismological data for the earthquake region are used as input data and boundary conditions for modeling. In this work it is shown that the main rupture arising at the origin of the earthquake is generated in a zone of high stress intensity at a certain ratio of the main tectonic stresses and propagates through areas of anomalously high stress concentration, causing maximum displacements in these zones. The results provide new insights into the focal mechanism of an earthquake, aimed at predicting the location and magnitude of strong crustal earthquakes in earthquake-prone areas. [ABSTRACT FROM AUTHOR]