ABSTRACT
The empirical approaches to estimate the crustal stresses are based on some empirical formulas utilizing stress measurements in various engineering projects and some earthquake prediction studies. In-situ stress measurements involve using overcoring methods, such as the borehole deformation method, conically ended borehole method, hydrofracturing method and acoustic emission method. In addition to these methods, a stress inference method called fault striation method based on fault striations was also used. The stress state of the Earth is of paramount importance in geomechanics and geophysics. Particularly, the virgin stress state in the Earth’s crust is of great interest in mining and civil engineering since the stability of excavations is very much influenced by that. Many in-situ stress inference techniques are classified into broadly direct or indirect techniques. Indirect stress inference techniques utilizing borehole breakouts, fault striations and earthquake focal mechanism solutions are also proposed and used. Numerical analyses clearly indicate local high-tensile stresses in the closed vicinity of the borehole end.
