SIMULATING ALONG-STRIKE INTERACTION BETWEEN LATERALLY OFFSET FAULTS: A NEW PHYSICAL MODELING APPROACH

Interaction between laterally offset faults (pull-apart basins between strike-slip faults or relay zones between normal faults) has traditionally been modeled experimentally using basal sheets or plates whose edges act as velocity discontinuities triggering the formation of laterally offset faults in the overlying brittle layer. This design, however, cannot be confidently applied to settings where the brittle layer overlies a weaker, viscous layer (e.g., upper/lower crust, or sediments/evaporites) because the basal plates are rigid and effectively much stronger than the model itself. We introduce an alternative design that allows simulating properly the interaction between laterally offset faults without the above caveat. In this new design small ridges at the brittle-ductile interface nucleate normal faults in the overlying brittle layer without interfering with their subsequent along-strike propagation. This design also allows fault blocks to subside, rise or rotate during deformation. Unlike in experiments using a basal sheet, faults in these new models are free to interact with one another. Results are markedly different from those from previous models in terms of relay-zone size, structural style, and fault geometry.