Ferdinand K. Oberle Cordell Johnson Joshua Logan Curt D. Storlazzi 2025 comma-delimited text data release doi:10.5066/P1QPSVMZ Pacific Coastal and Marine Science Center, Santa Cruz, California U.S. Geological Survey Suggested Citation: Oberle, F.K., Johnson, C., Logan, J.B., Storlazzi, C.D., 2025, USGS Nearshore Electrical Resistivity Tomography (ERT) profile data, Ofu, American Samoa: U.S. Geological Survey data release, https://doi.org/10.5066/P1QPSVMZ. https://doi.org/10.5066/P1QPSVMZ https://www.sciencebase.gov/catalog/item/67cb2b30d34ed37377098966 Along-shore surface-based 2D electrical resistivity tomography (ERT) surveys were collected in the nearshore region of Ofu, American Samoa. Profiles of resistivity on the shoreline will be used to assess the potential for terrestrial groundwater intrusion on the reef and the sources and fate of these water masses. Additional information about the field activity from which these data were derived is available online at: https://cmgds.marine.usgs.gov/fan_info.php?fan=2020-620-FA Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. 20200130 20200205 ground condition at time data were collected Complete None planned -169.666836 -169.657184 -14.180402 -14.184693 ISO 19115 Topic Category biota geoscientificInformation Global Change Master Directory (GCMD) THERMOCLINE CORAL REEFS Data Categories for Marine Planning Water Column Features USGS Thesaurus time series datasets electrical resistivity tomography ERT surveying resistivity Marine Realms Information Bank (MRIB) keywords physical oceanography None U.S. Geological Survey USGS Coastal and Marine Hazards and Resources Program CMHRP Pacific Coastal and Marine Science Center PCMSC USGS Metadata Identifier USGS:67cb2b30d34ed37377098966 Geographic Names Information System (GNIS) Ofu Papaloloa Point Fatuana Point South Pacific Ocean Territory of American Samoa None National Park of American Samoa American Samoa Polynesia region No restrictions or legal prerequisites for accessing the dataset. 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. Please recognize and acknowledge the U.S. Geological Survey as the originator(s) of the dataset and in products derived from these data. 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 831-460-4747 pcmsc_data@usgs.gov Raw data from the resistivity array were processed using the manufacturers software, AGI Earth Imager, on a Dell Personal Computer running Windows 11 Operating System. No formal attribute accuracy tests were conducted. Data fall within expected ranges. Dataset is considered complete for the information presented, as described in the abstract. Users are advised to read the metadata for each part of this data release carefully for additional details. A formal accuracy assessment of the horizontal positional information in the data set has not been conducted. Latitude and longitude were only measured at the beginning and ending of the ERT transect, and as such, horizontal coordinates are not available at each transect point. However, the transect is a straight line, and the distance of each point along the transect was measured by tape measure. The stated accuracy of the GPS unit used to determine the beginning and ending of the ERT transect is +/- 5m. Surface-based 2D Electrical Resistivity Tomography (ERT) surveys were conducted alongshore at the shoreline for one week in late January and early February of 2020 using a SuperSting R8 (AGI, Austin, Texas, USA) and cable with 56 electrodes at 2-m spacing. A dipole-dipole (DD) array was used with a max n-spacing of 7. 20240804 Resistivity data were processed using the manufacture’s software, AGI Earth Imager, and data exported to comma-delimited text files. 20241021 Point 0.00000001 0.0000001 Decimal degrees D_WGS_1984 WGS_1984 6378137.0 298.257223563 Table Comma-delimited table of a vertical profile of the resistivity of soil to electrical conductance. The first row contains column headers. Producer defined Distance_Along_Transect_(m) Along-transect distance of vertical resistivity profiles measured from the beginning lat/lon. Electrode spacing 0.0 110.0 meters 0.1 Depth_from_surface_(m) Depth below ground of resistivity measurement at each probe Producer defined -22.81 4.0 meters 0.1 Resistivity_(ohm m) Resistivity of soil to electrical conductance Producer defined 0.58 4127.03 Ohm meters 0.01 Latitude_(WGS) Latitude in decimal degrees of the beginning and ending of the survey transect line. Empty cells indicate the middle of the survey transect line where no positional data were collected. Global Positioning System -14.18469331 -14.18091509 decimal degrees 0.00000001 Longitude_(WGS) Longitude in decimal degrees of the beginning and ending of the survey transect line. Empty cells indicate the middle of the survey transect line where no positional data were collected. Global Positioning System -169.6668360 -169.6580912 decimal degrees 0.0000001 The first line of the csv file is a header line. Latitude and longitude were only measured at the beginning and ending of the ERT transect, and as such, horizontal coordinates are not available at each transect point. However, the transect is a straight line, and the distance of each point along the transect was measured by tape measure. U.S. Geological Survey U.S. Geological Survey - ScienceBase mailing and physical

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Denver CO 80225 1-888-275-8747 sciencebase@usgs.gov Two transect lines of resistivity data are available in comma-delimited csv format contained in a single zip file (Ofu20_ERT_Data.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. comma-delimited text 20180818 Zip file contains the csv tables. Windows users can use WinZIP to uncompress the files; Apple Macintosh users, Archive Utility; Linux and Unix users, gunzip. .03872 https://www.sciencebase.gov/catalog/file/get/67cb2b30d34ed37377098966 https://doi.org/10.5066/P1QPSVMZ Data can be downloaded using the Network_Resource_Name links. The first link is a direct link to download a zipped file of data and metadata. The second link points to a landing page with metadata and data for the entire data release. None. These data can be viewed with any text editor software. 20250429 U.S. Geological Survey, Pacific Coastal and Marine Science Center PCMSC Science Data Coordinator mailing and physical

2885 Mission Street

Santa Cruz CA 95060 831-460-4747 pcmsc_data@usgs.gov Content Standard for Digital Geospatial Metadata FGDC-STD-001-1998