REVISITING THE SEISMIC HAZARD CHARACTERIZATION OF THE TETON FAULT

The 62-km-long Teton fault is an east-dipping normal fault in western Wyoming that accommodates horizontal extension in the easternmost Basin and Range Province. Although the Teton fault has been the subject of seismotectonic studies, questions remain regarding its basic paleoseismic history. At present, results from a single trench on the southernmost part of the fault provide evidence for two Holocene surface ruptures; however, questions remain regarding (1) the Holocene mean recurrence for the fault, (2) why the latest Pleistocene to early Holocene vertical slip rate appears to exceed that for the middle to late Holocene, and (3) whether structural complexities along the fault act as barriers to rupture. In this investigation, we revisit the existing Teton fault characterization using new high-resolution LiDAR data, and evaluate the fault in the context of three fault sections.

We use LiDAR data to map the fault along the eastern base of the Teton Range at 1:10,000 scale, refine its total length, and identify sites for future paleoseismic investigations. Our preliminary mapping reveals a longer and more complex scarp composed of short splays and antithetical faults than is currently depicted. The value of revised mapping is particularly evident near Phelps Lake, at the boundary of the southern and central sections of the fault, where a larger overlap zone between the northern and southern sections is recognized. At the southern end of the fault, we include an additional ~10 km of previously unmapped scarps, which yields a revised total fault length of ~72 km. Our evaluation reveals multiple possible trench sites, including a site near Leigh Lake which consists of at least three parallel, ~1–2-m-high fault scarps on a deglacial surface. Our preliminary scarp map, if combined with a paleoseismic chronology for northern part of the fault, would provide a basis for a revised seismic hazard characterization of the Teton fault.