Centrifuge models investigating the influence of transverse pre-existing weaknesses on continental rifting

We present the results of centrifuge experiments investigating the role of preexisting crustal discontinuity on continental rifting. Specifically, we reproduce inherited weaknesses, orthogonal to the rift trend and parallel to the extension direction, and analyze their influence on the evolution and architecture of extensional deformation in the inner part and at the margins of continental rift valleys. Four different models, with variable width of the pre-existing weakness are illustrated. The models show a significant influence exerted by the pre-existing anisotropy on rifting: specifically, the inherited weakness inhibits the development of large boundary faults at rift margins, which are instead replaced by gentle monoclines dipping toward the rift axis. Axial faults are “captured” by the inherited anisotropy and rotate towards the pre-existing weakness, which therefore produces an unusual structural pattern also in the axial zone. This influence is dependent on the initial width of the pre-rift anisotropy and becomes negligible when its scaled width is 20 km or less.