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Speaker: Dr. Ryan Thigpen
30 November, 2018 @ 3:30 pm - 4:30 pm
Department of Earth and Environmental Sciences
University of Kentucky
Title: “Extending and Erasing the Teton Fault”
Abstract: The two most recent fault ruptures along the Teton fault (Wyoming, USA) were interpreted as Mw = 6.8 and Mw = 7.1 events resulting from slip magnitudes of 1.3 m and 2.8 m at ~4,800 and 7,900 ka, respectively. If the slip rate (~0.16 mm yr-1) determined from these events is extrapolated to present-day, the Teton fault is capable of generating Mw = 7.0 earthquakes resulting from ~2 m of slip. Because of the seismic hazard potential, it is critical to understand the extent and structural linkage of the entire Teton fault, specifically the less well understood northern extent of the fault system. Recent apatite U-Th/He data collected along multiple subvertical transects in the Teton range indicate that: (1) fault motion first initiated near Mount Moran in the northern extent of the present mountain range and gets younger to the north and south, (2) minimum cumulative slip estimates (~6 km), when combined with traditional fault growth models, suggests that the Teton fault may have originally extended 30-100 km farther north than presently mapped, and (3) fault onset timing (15-13 Ma) indicates that the majority of slip accumulated across the Teton fault prior to encroachment of the Yellowstone hotspot. This new analysis indicates that the progressive eastward migration of the Yellowstone hotspot relative to stable North America obliterated the topographic expressions of the northern extent of paleo-Teton range. While the footwall relief has been erased, the fault may remain active between the northern extent of Jackson Lake and the southern boundary of the present-day caldera. A new NPS lidar dataset that covers this area shows evidence of multiple candidate active fault segments, recognized as scarps that transect and offset post-glacial Quaternary landforms. If these disparate segments form a single continuous fault zone that links with the presently-active Teton fault, the traditional interpretation of fault length (~60 km) would be extended by at least 15 km northward (min. 25% extension), thus yielding a substantial increase of potential seismic hazard. This contribution will discuss the results from a recent campaign to collect high resolution seismic reflection and sonar of Jackson Lake to determine if the main Teton fault connects with proposed northern fault segments recognized in lidar data to the north of Jackson Lake.