Detailed Mapping of the 1983 Borah Peak Earthquake Surface Rupture (Idaho, USA) Using a High-Resolution Digital Terrain Model Derived from 2019 Lidar Data

In this work, we refined and expanded the coseismic surface rupture map of the 1983 M6.9 Borah Peak earthquake coseismic rupture mapping at a scale of 1:500. While earlier work (DuRoss et al., 2019; Bello et al., 2020, 2021) used structure-from-motion (SfM) methods to construct digital elevation models (DEMs) derived from small uncrewed aerial systems (sUAS or drone) imagery, the resulting fault maps lacked full coverage of the 1983 rupture, especially in areas where vegetation obscured the rupture traces. To address this, we generated a high-resolution (0.5 m) digital terrain model (DTM) derived from 2019 lidar data. The lidar data were collected as part of the United States Geological Survey’s 3D Elevation Program (U.S.G.S., 2018). This dataset spans the majority of the rupture and allows for improved detection of small-scale ruptures and other tectonic features, particularly in forested areas. We accessed the lidar data using OpenTopography’s workflow (Speed et al., 2022; https://github.com/OpenTopography/OT_3DEP_Workflows). The original lidar point cloud resolution is 20 points/m2 with 4 points/m2 of ground-classified points. From the ground classified points, we produced the 0.5 m DTM with lastools’ Blast2DEM (Isenburg, 2019), which uses the triangular irregular network approach. We conducted mapping at a scale of 1:500. We focused on identifying the upper edge of the fault scarp, typically the most prominent and easily recognizable feature in the topographic data. We mapped only those surface ruptures that could be confidently attributed to faulting during the 1983 earthquake based on their sharp morphological expression and consistency with previously documented coseismic ruptures from field observations (e.g., Crone et al., 1987; DuRoss et al., 2019; Bello et al., 2021). We also identified and mapped older, more eroded fault scarps, characterized by smoother morphologies, likely reflecting surface deformation from prehistoric earthquakes postdating the Last Glacial Maximum (LGM), consistent with previous studies (Bello et al., 2021, 2022; DuRoss et al., 2019). In total, we mapped more than 800 fault traces, spanning ~40 kilometers.

[
  "010:12"
]

[
  "geospatial"
]