Elastic modeling of fault-driven monoclinal fold patterns

The traces of buried dip-slip faults are often reconstructed by assuming that they follow the plan-view patterns of the overlying monoclines and by interpolating between seismic profiles. To place constraints on such reconstructions, the uplift pattern produced by prescribed slip on a set of buried reverse faults is calculated, assuming that the overall plan-view fold pattern is determined by faulting-induced elastic strain, while inelastic relaxation and gravitation only modify the details of the finite cross-sectional geometry of the folds. Faults are represented by dislocation planes embedded in an elastic medium which is otherwise continuous and uniform. These assumptions are applied to the monoclines of the Negev (Israel), driven by high-angle reverse faults. A first model closely follows the existing structural map, which is based on field mapping and seismic profiles, and is characterized by long, continuous faults. Slip is taken as uniform and proportional to fault length. Such a model does not produce either the pattern or the relative structural elevation of the overlying monoclines, and in particular the observed fold-axis variations. In a second model, we introduce fault en-echelon discontinuities and slip gradients at fault terminations. Relative slip on faults underlying various structures is proportional to their observed structural elevations. These features produce a reasonable approximation of the overall observed structural configuration of the monoclines. It can thus be concluded that: (1) the overall patterns of fault-driven folds are determined by the (coseismic?) elastic strain field; (2) fault segmentation is a major cause of observed axis undulations of fault-driven folds; (3) finite dip slip offset at depth is proportional to the observed structural elevation; and (4) along-strike slip gradients account for variations of the structural elevation in that direction.