Fig. 5: Deformation of the models with a flat Moho topography and a laterally varying surface elevation (non-uniform distribution of gravitational body forces) and a flat Moho topography and a flat surface elevation (uniform distribution of gravitational body forces) since the late Eocene under the influence of basal tractions and free slip side boundaries.

a–c The evolution of crustal structure together with the magnitude of the plastic strain (failure) for the brittle upper crust at 30 Ma, 15 Ma, and end of the simulation at 0 Ma, respectively. Vectors represent the flow field through time. d–f The evolution of finite strain (values represent second invariant of strain tensor) magnitude at the brittle and ductile zones of the crust at 30 Ma, 15 Ma, and end of the simulation at 0 Ma, respectively. Note that in the experiment with a flat Moho topography and a laterally varying surface elevation the weakening and damage of the brittle upper crust and the resulting accumulated plastic strain and plastic shear zones produce basins and ranges. Necking centers in the crust remain active, and the conjugate shear zones are diffuse. Dips of the active shear zones remain high and no low-angle detachment fault or metamorphic core complex forms. g, h Similar to a–c but at 35 and 0 Ma, respectively. i, j Similar to d–f but at 35 and 0 Ma, respectively. Note that in the experiment with a uniform thickness crust there is no weakening and damage of the brittle upper crust in response to basal tractions at the base, free slip side boundary conditions, and uniform distribution of gravitational body forces. Hence, the crustal thickness experiences minimal defamation for the whole duration of our simulation. Experiments start at 36 Ma and evolve to 0 Ma. Stages of evolution are given in Ma.