Comparing the morphologic variability of jointed bedrock fault scarps across four different settings

Characterizing the style and tempo of individual geomorphic processes is essential to produce accurate quantitative models of landscape evolution. Isolating the effects and rates of specific geomorphic processes on landscape evolution is challenging, however, given the complexity of natural systems, where many processes can be active concurrently at highly variable spatial and temporal scales. Comparing sites at similar stages of evolution but in different settings can yield the morphologic signatures of specific processes, but complications remain in determining rates of processes and characterizing the overall evolution of the landform. Conversely, comparing sites of different stages in similar settings can inform the rate and style of overall morphologic change in a landform type, but finding adequate sample sites and identifying specific processes is difficult. The morphologic variability of a landform as a comparison metric could bridge the gap between these two approaches, allowing comparisons to be made between landforms at different stages of evolution and in different conditions. Here, we apply this method to address morphologic dating of fault scarps in jointed bedrock. We conducted fieldwork to collect high resolution topographic data in three regions with jointed bedrock-hosted normal fault scarps: two areas of southwest Iceland, the Volcanic Tablelands of California, and the flank of Medicine Lake Volcano (CA). We used a supervised learning algorithm to automatically classify fault-scarp topographic profiles and objectively quantify the morphologic variability of each scarp, leveraging hundreds of profiles across several scarps from each area. We hypothesize that young fault scarps show large morphologic variability, associated with initial faulting, which decreases as geomorphic processes begin to dominate over tectonics, but can increase again moderately with renewed tectonic activity. Further work to constrain the signature of geomorphic processes may permit morphologic variability to be used as a first-order proxy for the tectonic history of these fault scarps.