A newly-developed numerical model enables the investigators to consider the development and evolution of faults in models of continental extension. The model simulates an elastic-plastic-viscous medium that is capable of developing localized deformation approximating faults. Model simulations result in the development of an evolving system of faults. The investigators propose to examine the size and number of half-graben units across the model rifts, the size distribution of faulting and the relative extension accommodated by large and small faults, the role of large rift-bounding faults, and the widening or narrowing of the active rift zone through time. They will focus on the Gulf of Suez rift for which there is an extensive database and expertise. They will also examine other rifts such as the East African rift, Anza trough, and Valencia trough, where available data document the pattern of faulting during rifting.