How does the orientation of a pre-existing basement weakness influence fault development during renewed rifting? Insights from three-dimensional discrete element modeling

We use three-dimensional discrete element modeling to investigate how the strike angle (α) of a pre-existing weak fault controls its reactivation potential, style and subsequent effect on the nearby fault network during extension. The pre-existing fault shows three reactivation modes: (i) full reactivation (α≥60°); (ii) partial reactivation (α=45°); and (iii) little or no reactivation (α=30°). A fully reactivated fault decreases the density, affects the orientation, and enhances the length and displacement of adjacent new faults. A partially reactivated fault generates some isolated fault segments along strike, and also influences fault orientation. However, when the pre-existing fault is not reactivated, its presence has little effect on the growth of new faults. Our study confirms that the reactivation pattern of a pre-existing fault and its influence on new fault growth varies with its strike angle relative to the extension direction. It improves our understanding of the variety in fault geometry, fault interaction style and the fault network above a weak pre-existing fault due to changing strike directions of the pre-existing fault. It also shows that a pre-existing fault influences adjacent fault geometry and the fault network by changing the density, orientation, length and displacement of newly formed faults. This work helps understanding three-dimensional fault geometries, the distribution and evolution of fault networks in rift basins affected by pre-existing faults, and predicting the extension direction of renewed rifting.