Development, deformation style, and seismic hazard of large normal faults

Young rifts such as the Malawi Rift System, located at the southern end of the East African Rift System, are a natural laboratory for how continents begin to break apart. Extension is typically accommodated by earthquakes within the upper crust. However, where extension occurs at a slow rate, the small number of historically recorded earthquakes likely provides an incomplete view of the potential magnitude range of events, limiting seismic hazard knowledge and the understanding of rift dynamics. Geological and geomorphological studies of faults scarps may help understand how faults develop, structurally evolve and accommodate displacement. Thus, in this thesis, using field and satellite observations of fault scarps, alongside numerical models, I develop a number of new methodologies in order to better understand young rift evolution. I show that the coseismic stress change between two active parallel faults influences whether the faults link, and the linkage style is determined by the distance between the faults. I also show that the orientation of a major border fault in a young rift can be influenced by local stresses and/or weakness at depth, forming faults oblique to what is expected by the regional stress field. Lastly, I identify segmentation on several Malawi Rift System faults from variations in scarp height and steps in the fault traces, and show that the morphology of each can be used to infer the number of prehistoric earthquake events. My work may suggest that large, normal faults in young rifts develop through a specific growth model, and that they can host earthquakes larger in magnitude than historically recorded. This research can help better understand rift evolution and earthquake hazard in the Malawi Rift System, as well as other regions where normal faults have the potential to cause large magnitude earthquakes, such as the Rukwa rift, Baikal rift and the Basin and Range Province