Figure 2
From: The surge of earthquakes in Central Oklahoma has features of reservoir-induced seismicity
The conceptual model of underground reservoir-induced seismicity (URIS) and pressure and stress solutions. (A) Salt water disposal (SWD) wells (black bars) inject into the highly permeable Arbuckle aquifer (grey-blue square). As the basement has a low permeability, the injected fluid forms an effective layer of height Δh (blue layer) on top of the basement (dark grey). Such a scenario can be considered as the filling of an underground reservoir. Caused by the weight of the water column and the pore-fluid pressure beneath Δh, stress- and pressure changes penetrate the poroelastic basement (dashed orange and blue lines, respectively). The perturbation of the ambient stress state may cause shear failure of pre-existing, optimally oriented, critically stressed faults. Changes of pressure (B) and stress (C,D) as profiles along the depth for times 24 h, 2 a and 5 a (colour-coded from light to dark) obtained from the analytic solution (black dots) and FEM (solid lines) for a constant boundary condition p0. Pore-fluid pressure profiles are marked by the distinct diffusion-like shape of the profile. With increasing time, the pressure in the medium increases. The maximum principal stress σ1 acts in vertical direction and is constant with time. In contrast, the minimum principal stress σ3 is horizontally oriented and time-dependent.
