COMBINING CHIRP SEISMIC REFLECTION AND LIDAR DATA TO UNDERSTAND THE STRUCTURAL ARCHITECTURE AND SLIP PARTITIONING OF THE NORTHERN TETON FAULT NEAR JACKSON LAKE, WYOMING

The Teton fault, an active normal fault in northwest Wyoming, presents a substantial seismic hazard for northwestern Wyoming. Recent thermochronologic studies suggest total slip magnitudes of 6-9 km total over the last 13 Ma. On the east side of the Teton Range, the fault offsets post-Pinedale (~14 Ka) glacial moraines by up to 12 m and older lateral moraines by 27-36m. Despite the hazard potential, the structural architecture and spatial extent of the northern Teton fault remains less well understood. Preliminary analysis of a recently collected CHIRP seismic reflection survey of Jackson Lake combined with publicly available LiDAR data from the National Park Service indicates that, at least in northern part of the Teton Range, Teton fault motion may actually be portioned into slip on a complex system of synthetic and antithetic faults exposed in preserved beneath the lake surface and onshore.

Our initial data shows that the upper crustal expression of the Teton fault is most likely segmented along strike, possibly as a result of the variable mechanical stratigraphy that ranges from the bedrock scarps preserved onshore to the lake muds preserved in structurally controlled depocenters. ArcGIS and Seisware interpretation software were used to measure fault offset along the surface and lake bed. High-resolution CHIRP seismic mapping of the 103 km² Jackson Lake shows a segmentation of the Teton fault propagating offshore into the lake bed as east dipping fault segments that may be connected on shore south of Jackson Lake via relay ramps. This segment has only been theorized before, but we find that high resolution seismic data confirms the fault splay exist. The preliminary seismic data also indicates a major series of west dipping antithetic faults which may control the edges of the Jackson Lake depocenters. Initial slip measurements suggest that the portion of the fault in the lake has a larger offset than the onshore expression and is a major influence on bathymetry.