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Fig. 1 | Geothermal Energy

Fig. 1

From: An open-access stress magnitude database for Germany and adjacent regions

Fig. 1

Explanation of the stress tensor. a The nine components of the stress tensor describe the stress state at an arbitrary point and enable calculation of the stress vector on any surface through that point. To describe the stress tensor components, an infinitely small cube with unit surfaces is used. b Due to the conservation of momentum (no rotation), the stress tensor is symmetric, and thus a coordinate system exists where shear stresses vanish along the faces of the cube. In this principal axis system, the remaining three stresses are the principal stresses. c Assuming that the vertical stress in the Earth’s crust \(S_\text {V} = \rho \cdot g \cdot z\) (g is gravitational acceleration, \(\rho\) is the rock density, z is the depth below surface) is a principal stress, \(S_\text {hmin}\) and \(S_\text {Hmax}\) are also principal stresses. This so-called reduced stress tensor is fully determined by four components: the \(S_\text {Hmax}\) orientation and the magnitudes of \(S_\text {V}\), \(S_\text {Hmax}\), and \(S_\text {hmin}\)

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