Fig. 7
From: Reactivation of variably sealed joints and permeability enhancement in geothermal reservoir rocks
Post-deformation microstructure. Photographs of samples following deformation (a, d, g). \({\sigma }_{1}\) denotes the direction of the applied axial load during deformation. Scanning electron microscope (SEM) images showing experimentally induced fractures in the rock matrix (b, e, h) and joints (c, f, i) of the studied sandstones. a, b, c Couches Intermédiaires (Box 117); d, e, f Couches de Karlstal (Box 179); g, h, i Couches de Trifels (Box 388)