Christopher B. DuRoss 20250312 1.0 vector digital data DuRoss, C.B., 2025, Priority faults for improving seismic hazard models in the Intermountain West region, version 1.0: U.S. Geological Survey data release, doi:10.5066/P13XVWR7. https://doi.org/10.5066/P13XVWR7 This data release includes a list of high-priority hazardous faults and associated spatial data for the Intermountain West (IMW) region of the United States. These are the top five faults or regions of concern per IMW state, based on the 2025 (version 1.0) meeting of the Basin and Range Province Earthquake Working Group (BRPEWG). In general, the list includes important, understudied faults where additional research would help to improve regional earthquake rupture forecasts and hazard modeling, reduce earthquake risk, and expand our knowledge of earthquake processes in the IMW region. This information will be used to guide IMW-specific priorities for research included in the USGS Earthquake Hazards Program external research priorities. Data were compiled to support the USGS National Seismic Hazard Model and guide External Research funding decisions. 2025 ground condition Complete Annually Intermountain West -121.7285 -103.9746 48.9225 31.5785 None Fault Earthquake Priority faults National Seismic Hazard Model USGS External Grants USGS Thesaurus earthquakes earthquake hazards scientific interpretation geospatial datasets geomorphology geochronology paleoseismology USGS Metadata Identifier USGS:67912c5ad34ea6a4002bf899 None Intermountain West United States None. Please see 'Distribution Info' for details. None. Users are advised to read the dataset's metadata thoroughly to understand appropriate use and data limitations. GHSC Data Steward U.S. Geological Survey, Geologic Hazards Science Center Open Data Policy coordinator mailing and physical

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Golden CO 80401 303-273-8500 ghsc_metadata@usgs.gov Dataset compiled by Christopher DuRoss (USGS), with contributions from: Arizona: Jeri Ben Horin, Arizona Geological Survey Colorado: James McCalpin, GEO-HAZ Consulting, Inc., Enrique Chon, Colorado Geological Survey Idaho: Zach Lifton, Idaho Geological Survey Montana: Yann Gavillot and Mike Stickney, Montana Bureau of Mines and Geology New Mexico: Dan Koning, New Mexico Bureau of Geology & Mineral Resources, New Mexico Institute of Mining & Technology Nevada: Richard Koehler, Nevada Bureau of Mines and Geology, University of Nevada, Reno Oregon: Lalo Guerrero, Oregon Department of Geology and Mineral Industries Wyoming: James Mauch, Wyoming State Geological Survey Utah: Adam Hiscock, Rachel Adam, Utah Geological Survey No accuracy tests were conducted. Data fields match details provided. This data release includes a list of high-priority hazardous faults and associated spatial data for the Intermountain West (IMW) region of the United States. These are the top five faults or regions of concern per IMW state, based on the 2025 (version 1.0) meeting of the Basin and Range Province Earthquake Working Group. Additional, lower priority faults (e.g., those included in the USGS Quaternary fault and fold database of the United States or the National Seismic Hazard Model) are not included in this dataset. No accuracy tests were conducted. No accuracy tests were conducted. State representatives provided lists of the top five faults or regions of concern in their states. Criteria for inclusion varied by state but mostly followed three themes: (1) High-risk faults, such as those crossing or proximal to urbanized regions or critical facilities. (2) Faults or regions lacking adequate characterization for seismic or displacement hazard analyses (e.g., 3D fault geometry, paleoearthquake history, or slip rate). (3) Faults that can facilitate regional or topical earthquake research, such as characterizing faults in an unstudied region or advancing our understanding of earthquake rupture behavior. In general, these are important, understudied faults and regions, where additional research would help to improve hazard modeling, reduce risk, and expand our knowledge of earthquakes in the IMW. Individual fault traces or grouped faults from the USGS or state-specific fault databases were buffered using a ±2.5 km distance. Regional polygons are also included, as provided by IMW state representatives. 20250228 Vector Area point 45 1 1 Decimal degrees North_American_Datum_1983 WGS_1984 6378137.0 298.257222101 IMW_priority_faults_regions.csv Comma Separated Value (CSV) file containing data. Producer Defined Name Name of the IMW fault, grouped faults, or region. For example, Sawatch fault (individual fault), San Andres fault system (grouped faults), and Uncompahgre Plateau region faults (region). Fault naming convention follows the USGS Quaternary fault and fold database of the United States (Qfaults; USGS, 2025); regional names provided by BRPEWG state representatives. Producer Defined Text Type Type of polygon. Fault – individual fault; grouped fault – one or more faults grouped; region – area of distributed faulting or general area of concern. Producer Defined Fault Individual fault Producer defined Grouped faults Group of two or more faults Producer defined Region Area of distributed faulting or general area of concern Producer defined Faults Faults included in a regional polygon or set of grouped faults. For example, the Cache Valley region faults include the East Cache and West Cache faults; the San Andres fault system includes the San Andres Mountains and Organ Mountain faults. For individual faults, this field is NULL. Producer Defined NULL No Data Producer defined Text State State within which the majority of the fault, grouped faults, or region is located. Producer Defined Text Source Source of spatial data. “Buffered USGS Qfaults traces” indicates USGS Quaternary fault and fold database (USGS, 2025) fault traces with a 2.5-km-wide buffer added. Other sources of data, including regional polygons, are provided. Producer Defined Text Notes Short statement provided by BRPEWG state representatives and only included in the csv file. This field includes justification for the priority fault designation, information on data gaps or remaining questions, and/or how additional research would help characterize hazard and reduce risk in the IMW region. Producer Defined Text NSHM Whether the fault or faults are included as earthquake sources in the 2023 update of the USGS National Seismic Hazard Model (Hatem et al., 2021). Partial – some but not all faults within a region or fault grouping are included in the model. Producer Defined Yes Fault included in USGS National Seismic Hazard Model Producer defined No Fault not included in USGS National Seismic Hazard Model Producer defined Partial Some but not all faults within a region or fault grouping are included in the National Seismic Hazard Model Producer defined IMW_priority_faults_regions_2025.shp Attribute Table Table containing attribute information associated with the data set. Producer Defined FID Internal feature number. ESRI Sequential unique whole numbers that are automatically generated. Shape Feature geometry. ESRI Shape type. Name Name of the IMW fault, grouped faults, or region. For example, Sawatch fault (individual fault), San Andres fault system (grouped faults), and Uncompahgre Plateau region faults (region). Fault naming convention follows the USGS Quaternary fault and fold database of the United States (Qfaults; USGS, 2025); regional names provided by BRPEWG state representatives. Producer Defined Text Type Type of polygon. Fault – individual fault; grouped fault – one or more faults grouped; region – area of distributed faulting or general area of concern. Producer Defined Fault Individual fault Producer defined Grouped faults Group of two or more faults Producer defined Region Area of distributed faulting or general area of concern Producer defined Faults Faults included in a regional polygon or set of grouped faults. For example, the Cache Valley region faults include the East Cache and West Cache faults; the San Andres fault system includes the San Andres Mountains and Organ Mountain faults. For individual faults, this field is NULL. Producer Defined NULL No Data Producer defined Text State State within which the majority of the fault, grouped faults, or region is located. Producer Defined Text Source Source of spatial data. “Buffered USGS Qfaults traces” indicates USGS Quaternary fault and fold database (USGS, 2025) fault traces with a 2.5-km-wide buffer added. Other sources of data, including regional polygons, are provided. Producer Defined Text NSHM Whether the fault or faults are included as earthquake sources in the 2023 update of the USGS National Seismic Hazard Model (Hatem et al., 2021). Partial – some but not all faults within a region or fault grouping are included in the model. Producer Defined Yes Fault included in USGS National Seismic Hazard Model Producer defined No Fault not included in USGS National Seismic Hazard Model Producer defined Partial Some but not all faults within a region or fault grouping are included in the National Seismic Hazard Model Producer defined Spatial data for IMW faults and regions of concern are included with this data release. Faults (e.g., the Wasatch fault zone), grouped faults (e.g., the Sawtooth–Boulder Front faults), and regions (e.g., faults within the Uncompahgre Plateau region) are represented as polygons and organized into a single geographic information systems (GIS) file in both shapefile and Google Earth keyhole markup language (kml) formats. For individual or grouped faults, a polygon forming a 2.5-km-wide buffer (5 km total width) around the Qfaults trace is provided. Polygons for regional areas are also included and intended to represent areas of interest and/or distributed faulting. Justification for priority faults and regions is included in a plain text, commas-separated values (csv) file. DuRoss, C.B., 2025, Priority faults for improving seismic hazard models in the Intermountain West region, version 1.0: U.S. Geological Survey data release, doi:10.5066/P13XVWR7. U.S. Geological Survey - ScienceBase mailing address

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Denver CO 80225 1-888-275-8747 sciencebase@usgs.gov Unless otherwise stated, all data, metadata and related materials are considered to satisfy the quality standards relative to the purpose for which the data were collected. Although these data and associated metadata have been reviewed for accuracy and completeness and approved for release by the U.S. Geological Survey (USGS), no warranty expressed or implied is made regarding the display or utility of the data for other purposes, nor on all computer systems, nor shall the act of distribution constitute any such warranty. Digital Data https://doi.org/10.5066/P13XVWR7 None 20250312 GHSC Data Steward U.S. Geological Survey, Geologic Hazards Science Center Open Data Policy coordinator mailing and physical

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Golden CO 80401 303-273-8500 ghsc_metadata@usgs.gov FGDC Biological Data Profile of the Content Standard for Digital Geospatial Metadata FGDC-STD-001.1-1999