GeoEarthScope LIDAR SURVEY ALONG THE NEPHI SEGMENT, WASATCH FAULT, UTAH

The GeoEarthScope program of the National Science Foundation collected high-resolution LIDAR topography data in the western US during the fall of 2007 and summer of 2008. Surveys were flown along active faults in California, the Nephi segment of the Wasatch Fault, the Teton Fault, over several sites in Yellowstone National Park, in Washington State, and along the eastern Denali Fault in Alaska. The data sets include both unfiltered and filtered elevation grids posted at 0.5m, together with point cloud files. All data will be released to the scientific community and public for use in basic research and geological hazards applications via the web portal OpenTopography.org. The Nephi segment of the Wasatch Fault was selected as a show case for normal fault-related geomorphology. Geomorphic features include fault scarps that cut alluvial fans of a variety of ages, the presence of several large landslides that extend across the fault, and debris flow deposits that affect suburban developments. This data set provides the opportunity to further refine and explore the paleoseismic history of the segment. Three dimensional computer visualizations of the high resolution topography allow further refinement of fault scarp, landslide and debris flow maps together with quantitative measurements of slope, aspect, surface roughness and displacement over a wide range of scales. Measurements of vertical fault displacement can be made with decimeter relative accuracy over lateral distances of hundreds of meters to several kilometers, providing the opportunity to explore statistical aspects of along-strike displacement variability, and interactions between single and multiple fault-strands within the segment. One can also evaluate subtle geomorphic effects of faulting, such as knick point migration in fluvial channels, and tilting of alluvial fan complexes caused by lateral variations in fault offset or the presence of subsurface subsidiary fault splays. Several examples of these applications will be presented, together with an evaluation of data set accuracy to help guide future applications for geological hazards and process geomorphology studies.