LIDAR-BASED MAP OF AN ACTIVE, NORMAL FAULT: TETON FAULT, WYOMING

Bare earth LiDAR data (<1 m resolution) are used to create a new map of the Teton fault, an active normal fault along the west side of Teton National Park, Wyoming. Data were collected by EarthScope and downloaded from OpenTopography. There are several differences between our LiDAR-based map and previously published maps of the Teton fault.

LiDAR data can provide high resolution topographic models of earth’s surface as if it were stripped of vegetation and is used to analyze subtle changes in surface topography. Bare earth data are particularly useful for mapping fault scarps and subtle synthetic and antithetic splays that are typically obscured by vegetation or otherwise unrecognized. To elicit the primary and secondary scarps of the Teton fault, we applied four different GIS analyses (hillshade, slope, aspect and contour) and adjusted colors, stretch and lighting to further enhance the fault-related lineations. Each analysis provides a unique way to view the scarps, and together they strengthen our interpretations. The primary fault is expressed as a large north-south striking, eastward dipping linear feature on the eastern edge of the Teton Range; offset on the scarp varies along strike, but can be as great as 30 m. The scarps of synthetic splays are small linear features with similar strike and dip to the primary fault; antithetic splays are small, similar-striking, reverse-dipping lineations.

Our analysis of the LiDAR data also revealed several previously unmapped landslides, many of which obscure the primary fault scarp and resulted in some of the fault discontinuities found on previous maps. Further research will be conducted this summer to field verify the existence of the fault splays and to analyze some of the more complicated areas.

Accurately mapping normal faults and their splays provides better measures of the amount of total fault slip and the continuous length of the fault as well as the location of the areas of highest slip, overlaps, and stepovers. These data are used to develop accurate hazard analysis models. The data gathered also provide details on the interaction between the primary fault and earth’s surface, which may lead to a better understanding of near-surface fault mechanics and the formation of antithetic and synthetic splays.