Onset of slip partitioning under oblique convergence within scaled physical experiments

Oblique convergent margins host slip partitioned faults with simultaneously active strike-slip and reverse faults. Such systems defy energetic considerations that a single oblique-slip fault accommodates deformation more efficiently than multiple active faults. Previous experiments in dry sand demonstrate that strike-slip faults can develop after bi-vergent thrusting but the processes that foster two slipping faults rather than one remain elusive. Some slip partitioned systems may develop at margins that previously accommodated transform deformation; the vertical fault cannot accommodate contraction so that growth of a new thrust fault results in slip partitioning. We use scaled experiments within wet kaolin combined with digital image correlation techniques to map deformation at the onset of slip partitioning in low convergence (< 30 ̊) experiments with and without a pre-existing vertical weak plane.