Name the sources of horizontal stresses.

Name the sources of horizontal stresses.

• A. Thermal expansion and contraction
• B. Poisson's Ratio Effect and Tectonic Stresses
• C. Hydraulic pressure
• D. Capillary pressure

Answer: (B)

Horizontal stresses come from two main mechanisms. First, the tectonic stress field produced by plate movements that compress or shear rocks in the horizontal directions. Second, the Poisson effect: when vertical loading from the overburden compresses the rock, the material tends to contract vertically but, if lateral expansion is constrained, develops horizontal stresses as a byproduct of the elastic response. These two sources together explain why horizontal stresses can be substantial even without direct horizontal forcing. Hydraulic pressure acts in the pore space and can influence effective stress, but it is not a bulk source of horizontal geostress. Capillary pressure is an interfacial pore-scale pressure between fluids and does not establish a large-scale horizontal stress field. Thermal expansion or contraction can cause transient stresses if temperature changes are constrained, but they are not the primary sustained sources of horizontal stresses in the crust.

Horizontal stresses come from two main mechanisms. First, the tectonic stress field produced by plate movements that compress or shear rocks in the horizontal directions. Second, the Poisson effect: when vertical loading from the overburden compresses the rock, the material tends to contract vertically but, if lateral expansion is constrained, develops horizontal stresses as a byproduct of the elastic response. These two sources together explain why horizontal stresses can be substantial even without direct horizontal forcing.

Hydraulic pressure acts in the pore space and can influence effective stress, but it is not a bulk source of horizontal geostress. Capillary pressure is an interfacial pore-scale pressure between fluids and does not establish a large-scale horizontal stress field. Thermal expansion or contraction can cause transient stresses if temperature changes are constrained, but they are not the primary sustained sources of horizontal stresses in the crust.