Jenna C. Hill 20260527 polyline shapefile data release DOI:10.5066/P1M8N8CT Pacific Coastal and Marine Science Center, Santa Cruz, CA U.S. Geological Survey Suggested Citation: Hill, J.C., 2026. Submarine slope failure scarps along the Cascadia subduction zone: U.S. Geological Survey data release, https://doi.org/10.5066/P1M8N8CT. https://doi.org/10.5066/P1M8N8CT Seafloor features identified as headward eroding mass failure scarps were digitized by hand from high-resolution multibeam bathymetry compilations (30 meter grids) across the Cascadia subduction zone, which spans the region offshore of northern California, Oregon and Washington. These features were initially published by Hill and others (2022; https://doi.org/10.1016/j.epsl.2022.117797) and here were present an updated version of this dataset. The interpretation of these seafloor failure scarps was conducted to investigate the spatial distribution of slope failure along the Cascadia subduction zone and identify potential source areas for earthquake-triggered landslide deposits, turbidity currents and other associated mass transport deposits. This work is part of a larger USGS Subduction Zone Marine Geohazards project that aims to assess potential offshore earthquake, submarine landslide and tsunami hazards along U.S. subduction zones. The data are intended for research purposes and can be used with geographic information systems (GIS) software. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Although this Federal Geographic Data Committee-compliant metadata file is intended to document the dataset in nonproprietary form, as well as in Esri format, this metadata file may include some Esri-specific terminology. 1994 2023 Range of time during which multibeam bathymetry source data was collected. Planned As needed -127.310465 -124.349509 48.821788 40.395562 USGS Metadata Identifier USGS:c82b4da2-e1ae-45c6-908b-94934a425104 ISO 19115 Topic Category oceans geoscientificInformation USGS Thesaurus geospatial datasets hazards marine geology marine geophysics multibeam sonar scientific interpretation sea-floor characteristics Marine Realms Information Bank (MRIB) keywords subduction zone accretionary wedge landslide geological features None U.S. Geological Survey USGS Coastal and Marine Hazards and Resources Program CMHRP Pacific Coastal and Marine Science Center PCMSC Geographic Names Information System (GNIS) United States of America State of California State of Oregon State of Washington Pacific Ocean No access constraints USGS-authored or produced data and information are in the public domain from the U.S. Government and are freely redistributable with proper metadata and source attribution. These data are marked with a Creative Common CC0 1.0 Universal License. Please recognize and acknowledge the U.S. Geological Survey as the originator(s) of the dataset and in products derived from these data. This information is not intended for navigation purposes. U.S. Geological Survey, Pacific Coastal and Marine Science Center PCMSC Science Data Coordinator mailing and physical

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Santa Cruz CA 95060 831-427-4747 pcmsc_data@usgs.gov seafloor_failure_scarps_cascadia_preview.jpg Quick view image of the seafloor failure scarps on the Cascadia margin JPEG Microsoft Windows 10 Version 10.0 (Build 22631); Esri ArcGIS 13.5.5.57366 Jenna C. Hill Janet T. Watt Daniel S. Brothers 2022 Hill, J.C., Watt, J.T., Brothers, D.S., 2022. Mass wasting along the Cascadia subduction zone: Implications for abyssal turbidite sources and the earthquake record, Earth and Planetary Science Letters, 597: 117797. https://doi.org/10.1016/j.epsl.2022.117797 Jenna C. Hill Janet T. Watt Charles K. Paull David W. Caress Daniel S. Brothers Kevin Arizmendi Roberto Gwiazda Jared Kluesner Eve Lundsten Nora M. Nieminski Jason S. Padgett Jennifer B. Paduan George Snyder 2026 Hill, J.C., Watt, J.T., Paull, C.K., Caress, D.W., Brothers, D.S., Arizmendi, K., Gwiazda, R., Kluesner, J., Lundsten, E., Nieminski, N.M., Padgett, J.S., Paduan, J.B., Snyder, G., 2026. Widespread abyssal turbidites record megathrust earthquake-triggered landslides and coseismic deformation in the Cascadia subduction zone, Science Advances, 12:3. https://doi.org/10.1126/sciadv.adx6028 Ryuzo Yokoyama Michio Shirasawa Richard J. Pike 2002 Yokoyama, R., Shirasawa, M., Pike, R.J., 2002. Visualizing topography by openness: A new application of image processing to digital elevation models, Photogrammetric engineering and remote sensing, 68:3, 257-265. Tatsuro Chiba Shin-ichi Kaneta Yusuke Suzuki 2008 Chiba, T., Kaneta, S. I., & Suzuki, Y. (2008). Red relief image map: new visualization method for three dimensional data. The international archives of the photogrammetry, remote sensing and spatial information sciences, 37(B2), 1071-1076. https://www.isprs.org/proceedings/XXXVII/congress/2_pdf/11_ThS-6/08.pdf No formal attribute accuracy tests were conducted. No formal logical consistency tests were conducted. This dataset is compiled from available seafloor bathymetry data gridded at 30 m resolution. Our analysis encompasses all identifiable seafloor scarps that show geomorphic evidence of headward incision and downslope sediment movement. The resolution of the seafloor bathymetry source layers limits imaging of scarps with <10 m headscarp heights. Many of the features identified in this dataset likely represent composite failure scarps that are not readily distinguishable with the available seafloor bathymetry resolution. The mapped features are deemed to be accurate to a scale of 1:75,000 relative to the base layers. Horizonal accuracy of the shapefile features is tied to the horizonal positional accuracy of the source layers used as a base map to define the seafloor features. Refer to the source layers for positional accuracy (typically ~30 m). No vertical accuracy tests were conducted nor were applicable Dartnell, P. Rudebusch, J.A. Conrad, J.E. Watt, J.T. Hill, J.C. 2021 Raster Digital Dataset online U.S. Geological Survey https://doi.org/10.5066/P9C5DBMR Digital 1994 2023 Ground condition at time data were collected Southern Cascadia bathymetry compilation The southern Cascadia bathymetry compilation was used as a base layer to interpret headward eroding scarps on the seafloor. The resolution of the data limits imaging of scarps with <10 m headscarp heights. Dartnell, P. Watt, J.T. Hill, J.C. Conrad, J.E. 2023 Raster Digital Dataset online U.S. Geological Survey https://doi.org/10.5066/P9PERGFK Digital 1998 2021 Ground condition at time data were collected Central Cascadia bathymetry complication The central Cascadia bathymetry compilation was used as a base layer to interpret headward eroding scarps on the seafloor. The resolution of the data limits imaging of scarps with <10 m headscarp heights. Beeson, J. Dartnell, P. Watt, J.T. 2025 Raster Digital Dataset online U.S. Geological Survey https://doi.org/10.5066/P14SLWTD Digital 2006 2022 Ground condition at time data were collected Northern Cascadia bathymetry compilation The northern Cascadia bathymetry compilation was used as a base layer to interpret headward eroding scarps on the seafloor. The resolution of the data limits imaging of scarps with <10 m headscarp heights. Ryan, W.B.F. Carbotte, S.M. Coplan, J.O. O’Hara, A.M. Melkonian, A. Arko, R. Weissel, R.A. Goodwillie, A. Nitsche, F. Bonczkowski, J. Zemsky, R. 2009 Raster Digital Dataset online Lamont-Doherty Earth Observatory https://www.gmrt.org Digital 1992 2022 Ground condition at time data were collected GMRT The GMRT was used as a base layer to interpret headward eroding scarps on the seafloor. The resolution of the data limits imaging of scarps with <10 m headscarp heights. Mapping of seafloor failure scarp features was conducted using the multibeam bathymetry compilations listed in the Source Citations. In addition to seafloor depth values, we used bathymetric derivatives seafloor slope and topographic openness (for example, Yokoyama and others, 2002; Chiba and others, 2008 – see citations in Cross References) to discern more subtle features. Seafloor failure scarps are identified as arcuate, stepped, geomorphic features that disrupt the local slope and show evidence of evacuation zones. Seafloor features identified as headward eroding scarps were digitized by hand and characterized as either gully heads, defined as having narrow channels (<500 m wide) with evidence for headward erosion cutting into the seafloor at the top, or headscarps, defined as arcuate features that mark the upslope extent of mass wasting and typically have steep (>10 degrees) walls. These features were then classified by location, indicating their location within submarine canyon catchment systems or on the open slope. Southern Cascadia bathymetry compilation Central Cascadia bathymetry compilation Northern Cascadia bathymetry compilation GMRT 2026 Vector String 9634 .0003 .0003 Decimal degrees North American Datum of 1983 GRS80 6378137 298.257222101 seafloor_failure_scarps_cascadia.shp shapefile containing polylines representing slope failure scarps Producer defined FID internal feature number ESRI Sequential unique whole numbers that are automatically generated. Shape feature geometry ESRI shapefile feature type Type seafloor feature type Producer defined scarp Headscarps are arcuate features that mark the upslope extent of mass wasting and typically have steep (>10 degree) walls. Producer defined Gully Gully heads are narrow channels (<500 m wide) with evidence for headward erosion cutting into the seafloor at the top. Producer defined Location Location of the failure scarps on the seafloor Producer defined Canyon seafloor scarp or gully feature is located within a submarine canyon catchment system Producer defined Slope seafloor scarp or gully feature is located on the open slope outside of a submarine canyon catchment system Producer defined Zone Region encompassing the seafloor failure scarps Hill and others (2022) Southern Seafloor feature is located in the southern Cascadia region as defined by Hill and others (2022). Producer defined Central Seafloor feature is located in the central Cascadia region as defined by Hill and others (2022). Producer defined Northern Seafloor feature is located in the northern Cascadia region as defined by Hill and others (2022). Producer defined zipped file of polyline shapefile and associated files U.S. Geological Survey U.S. Geological Survey - CMGDS mailing and physical

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Santa Cruz CA 95060 831-427-4747 pcmsc_data@usgs.gov These data are available in shapefile format (seafloor_failure_scarps_cascadia.shp and associated files) contained in a single zip file (seafloor_failure_scarps_cascadia.zip) accompanied by CSDGM FGDC-compliant metadata. 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 on any other system or for general or scientific purposes, nor shall the act of distribution constitute any such warranty. Shapefile ArcGIS Pro 3.5.5 Esri polyline shapefile Zip file contains the interpreted polyline shapefile and the associated metadata. Zip files can be extracted using built-in utilities on Windows (Right-click the zipped folder and select Extract All to decompress files to a chosen location or double-click to browse contents) or Mac using the Archive Utility tool. 10.6 https://doi.org/10.5066/P1M8N8CT Data and metadata can using the Network_Resource_Name link and scrolling down to the Geologic Hazards Data section. None. These data can be viewed with GIS software. 20260527 U.S. Geological Survey, Pacific Coastal and Marine Science Center PCMSC Science Data Coordinator mailing and physical

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Santa Cruz CA 95060 831-427-4747 pcmsc_data@usgs.gov Content Standard for Digital Geospatial Metadata FGDC-STD-001-1998