Constant-thickness deformation above curved normal faults

Extensional fault systems are commonly described using models that assume layer-oblique heterogeneous simple shear deformation in fault blocks. These models are colloquially known as vertical or inclined shear models. Less commonly, layer-parallel heterogeneous simple shear is employed; these models are called constant-thickness/flexural-slip models, and have the geometric property that they conserve both bed length and bed thickness. Although popular, vertical or inclined shear models suffer from the limitation that they do not explain two widely observed features of extensional fault systems: crestal collapse grabens, and downwardly blind faults within the hanging wall. Currently used constant-thickness/flexural-slip models are severely limited by their inability to ‘forward-model’ faults with dips (angular bends) greater than 30°. We have modified the most widely used constant-thickness/flexural-slip model so that it can be applied to faults with dips or angular bends greater than 30°. The resulting model can be used to describe the constant-thickness geometry of hanging walls developed above normal faults of any shape. Alternatively, the model can be used to predict the amount and location of departures from constant-thickness (and constant bed length) deformation in a fault hanging wall, manifest at large-scale by crestal collapse grabens and downwardly blind faults, or at small-scale by sub-seismic-resolution faulting.