The pecularities of shear crack pre-rupture evolution and distribution of seismicity before strong earthquakes

Abstract

Abstract. Several methods are presently suggested for investigating pre-earthquake evolution of the regions of high tectonic activity based on analysis of the seismicity spatial distribution. Some precursor signatures are detected before strong earthquakes: decrease in fractal dimension of the continuum of earthquake epicenters, cluster formation, concentration of seismic events near one of the nodal planes of the future earthquake, and others. In the present paper, it is shown that such peculiarities are typical of the evolution of the shear crack network under external stresses in elastic bodies with inhomogeneous distribution of strength. The results of computer modeling of crack network evolution are presented. It is shown that variations of the fractal dimension of the earthquake epicenters' continuum and other precursor signatures contain information about the evolution of the destruction process towards the main rupture.

Dynamics of multifractal and correlation characteristics of the spatio-temporal distribution of regional seismicity before the strong earthquakes

“…That is an important condition for searching of the precursory phenomena using the methods suggested in this paper. In fact, the results of simulation of the destruction of elastic body with a number of cracks (Kiyashchenko and Troyan, 2001) indicate that such precursory tendencies as the decrease of correlation dimension or increase of the level of spatio-temporal correlation in the synthetic seismicity appeared due to interaction of growing cracks in wide range of scales.…”

“…At the large depths the material of the earth crust loses elasticity and the mechanisms of the deep earthquakes could be linked to phase transitions rather than to shear fracturing. The simulation of the destruction of elastic body with a number of shear fractures (see Kiyashchenko and Troyan, 2001) showed the certain dynamics of scaling characteristics and the level of spatio-temporal correlations in the synthetic seismicity prior to main rupture (see Sect. 1).…”

“…As it is discussed in the previous section, the multifractal approach is suitable for this purpose. Moreover, the variations of scaling characteristics of the seismicity have to contain information about the evolution of the destruction process in the earth crust (see Kiyashchenko and Troyan, 2001).…”

“…The results of numerical modeling of the destruction process (Kiyashchenko and Troyan, 2001) and the results of study of the acoustic emission (Sobolev and Ponomarev, 1999) show the increase of spatio-temporal correlations in the seismicity distribution before the main rupture.…”

“…The results of numerical modeling of the destruction process of the elastic body, containing a number of cracks (Kiyashchenko and Troyan, 2001), showed that correlation dimension of the continuum of the synthetic seismic- ity hypocenters decreased during evolution of the destruction process towards the main rupture. Hence, evolution of the inhomogeneity of spatial distribution of seismicity in different scales, which manifests itself in decrease of fractal dimensions, can be interpreted as a significant feature of the earthquake preparation process.…”