DOI: 10.5066/p1bqjfs2
title: Detailed Mapping of the 1983 Borah Peak Earthquake Surface Rupture (Idaho, USA) Using a High-Resolution Digital Terrain Model Derived from 2019 Lidar Data

description: 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.

This data release accompanies the manuscript entitled “Unveiling coseismic deformation from differenced legacy aerial photography and modern lidar topography: The 1983 M6.9 Borah Peak earthquake, Idaho, USA” by Chelsea P. Scott, Nadine G. Reitman, and Simone Bello

Field descriptions
For each fault trace (polyline), we assigned four attributes:
(1) “ID”: An identification number for reference and database organization.
(2) “TYPE”: Rupture type, distinguishing between “primary” and “distributed” ruptures. Primary ruptures exhibit greater coseismic displacement, continuity, and/or length, and are typically the sole rupture in areas of limited surface expression. Distributed ruptures (also called “secondary ruptures), by contrast, accommodate smaller displacements and may be either synthetic or antithetic to the main fault.
(3) “OBJECT”: This provides information about the mapped feature. The field values can be: "1983_Rupture" indicates that the mapped feature is a coseismic rupture confidently attributed to the 1983 earthquake. "Prehistoric Scarp" indicates that the feature is a tectonic scarp likely representing the cumulative displacement from multiple earthquakes. "Unk" indicates that it was not possible to determine the feature's origin with confidence.
(4) “SYN_ANT”:  Dip direction: synthetic ruptures (“SYN” in the shapefile attribute table) dip to the W-to-S, while antithetic (“ANT” in the shapefile attribute table) ruptures dip to the E-to-N, relative to the main trace of the Lost River Fault.

Vertical Separation (VS)
Also included in this data release are the vertical separation (VS) results (Scott_etal_2025_VS.csv) described in the above manuscript derived from vertical differencing of pre- and post-earthquake high-resolution topographic data. The vertical separation results are provided in CSV format. Column headers: X and Y are location in UTM Zone 12 (EPSG: 32612). Distance along strike is distance along strike of the 1983 surface rupture in meters (plotted in Figure 4 of the main manuscript). VS is vertical separation displacement in meters. DeltaVS is vertical separation displacement uncertainty in meters (calculated as described in the main manuscript).

References
Bello, S., Scott, C. P., Ferrarini, F., Brozzetti, F., Scott, T., Cirillo, D., et al. (2020). Database of vertical separation measurements along the Lost River Fault (Idaho - USA) from 1983 Mw 6.9 earthquake ruptures and Quaternary fault scarps [Application/zip]. PANGAEA. https://doi.org/10.1594/PANGAEA.921027

Bello, S., Scott, C. P., Ferrarini, F., Brozzetti, F., Scott, T., Cirillo, D., et al. (2021). High-resolution surface faulting from the 1983 Idaho Lost River Fault Mw 6.9 earthquake and previous events. Scientific Data, 8(1), 68. https://doi.org/10.1038/s41597-021-00838-6

Crone, A. J., Machette, M. N., Bonilla, M., Lienkaemper, J. J., Pierce, K., Scott, W., & Bucknam, R. (1987). Surface faulting accompanying the Borah Peak earthquake and segmentation of the lost river fault, central Idaho. Bulletin of the Seismological Society of America, 77. https://doi.org/10.1785/BSSA0770030739
 
DuRoss, C. B., Bunds, M. P., Gold, R. D., Briggs, R. W., Reitman, N. G., Personius, S. F., & Toké, N. A. (2019). Variable normal-fault rupture behavior, northern Lost River fault zone, Idaho, USA. Geosphere, 15(6), 1869–1892. https://doi.org/10.1130/GES02096.1
 
Isenburg, M. (2019). LAStools - Efficient tools for lidar processing. Retrieved from www.lastools.org

Speed, C., Beckley, M., Crosby, C. J., & Nandigam, V. (2022). Reproducible scientific workflows for accessing, processing, and visualizing USGS 3DEP lidar data. Retrieved from https://github.com/opentopography/OT_3DEP_Workflows
 
U.S. Geological Survey. (2018). Lidar Point Cloud - USGS National Map 3DEP Downloadable Data Collection. U.S. Geological Survey.