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Russian Geology and Geophysics

2013 year, number 2

STRESS AND DEFORMATION OF THE EARTH’S CRUST IN THE ALTAI-SAYAN MOUNTAINOUS AREA

Yu.L. Rebetsky, O.A. Kuchai, A.V. Marinin
Keywords: Tectonophysics, geodynamics, stresses, strains, faults, earthquake focal mechanisms, loading mechanisms
Pages: 206-222

Abstract

We present the results of tectonophysical reconstruction of natural stress of the Earth’s crust in the Altai-Sayan mountain region using cataclastic analysis of fault slips and seismic data on the focal mechanisms of earthquakes. This method allows one to obtain the parameters of the total stress tensor by invoking additional data: generalized experimental data on the brittle fracture of rocks, seismic data on the released stress of strong earthquakes, and data on the topography and density of rocks. The results of the tectonophysical reconstruction of stresses showed significant heterogeneity of the stress state, which is manifested not only in the variation of the strike and dip of the principal axes of the stress tensor, determining changes in the geodynamic regime of the Earth’s crust, but also in the close location of the regions of high and low isotropic tectonic pressure in relation to the lithostatic pressure. The variance of the ratio of tectonic pressure to lithostatic pressure is in the range of 0.59–1.31, with an average value for the region close to unity. This paper discusses internal or external mechanisms capable of generating the stress field obtained by the tectonophysical reconstruction.