In-Situ Stress State and Tectonic Regime in Different Depths of Earth Crust

Abstract

In this paper by consideration of tectonic conditions along with theoretical and empirical relationships, a new strategy for estimation of the variation range of lateral stress coefficients [K = 0.5(Sh + SH)/SV] at different depths is presented. Tectonic regime is the main factor affecting the in situ stress arrangement, and therefore, the lateral stress coefficient in the earth’s crust. Based on tectonic regimes and the associated in situ stress arrangements, the upper and lower bound of K value are determined in reverse and normal faulting tectonic regimes, respectively. Another limiting factor of in situ stress magnitudes and the K values at different depths is strength of the earth’s crust. The horizontal stresses in active tectonic regions are considered as the horizontal stress due to overburden loading and additional horizontal tectonic stresses (∆STec), therefore, horizontal stresses are assumed as combination of two main parts; first part depends on the depth and the second part is independent of the depth. Based on the results of this study, increase in horizontal stresses is due to the increasing in the overburden loading, while the additional tectonic stresses remain constant, is the main reason of the tectonic regime changes and resulted in a nonlinear decrease of K value with depth.