Christopher Galley Daniel Sorenson Isabelle M. Shapiro Amy Gartman 20260401 comma-delimited text data release DOI:10.5066/P1DRPIQK Pacific Coastal and Marine Science Center, Santa Cruz, California U.S. Geological Survey Suggested Citation: Galley, C., Sorenson, D., Shapiro, I.M., and Gartman, A., 2026, Magnetics Data from the Escanaba Trough (Gorda Ridge): U.S. Geological Survey data release, https://doi.org/10.5066/P1DRPIQK. https://doi.org/10.5066/P1DRPIQK This data release provides access to magnetics data collected by the AUV Sentry during the TN403 cruise in the Escanaba Trough (USGS Field Activity 2022-621-FA). These data serve to expand the knowledge and statistics for deep ocean marine mineral occurrences and composition within the global ocean. Additional information about the field activity or activities from which these data were derived is available online at: https://cmgds.marine.usgs.gov/fan_info.php?fan=2022-621-FA Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. 20220712 20260123 Magnetics data compiled and processed Complete None planned -127.5671 -127.4024 41.1735 40.6942 USGS Metadata Identifier USGS:5218d4c6-701d-4225-8cf2-9df71c99ca5c ISO 19115 Topic Category geoscientificInformation None U.S. Geological Survey USGS Coastal and Marine Hazards and Resources Program CMHRP Pacific Coastal and Marine Science Center PCMSC magnetic anomaly Data Categories for Marine Planning substrate Marine Realms Information Bank (MRIB) Keywords continental margin USGS Thesaurus magnetic field (earth) magnetometer measurement aeromagnetic surveying metallic mineral resources Geographic Names Information System (GNIS) Pacific Ocean NGA GEOnet Names Server (GNS) Escanaba Trough Gorda Ridge No access constraints. Please see 'Distribution Information' for details. 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 and the University of Ottawa as the originator(s) of the dataset and in products derived from these data. This information is not intended for navigation purposes. PCMSC Science Data Coordinator U.S. Geological Survey, Pacific Coastal and Marine Science Center mailing

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Santa Cruz CA 95060 831-427-4747 pcmsc_data@usgs.gov The data was processed on with Woods Hole Oceanographic Institute's full-vector calibration program, written by Dr. Maurice Tivey in MATLAB. MATLAB was operated on a Windows 10 system. Christopher Galley Peter G. Lelièvre Amir Haroon Sebastian Graber John Jamieson Florent Szitkar Isobel Yeo Colin G. Farquharson Sven Petersen Robert Evans 2021 Galley, C., Lelievre, p., Haroon, A., Graber, S., Jamieson, J., Szitkar, F., Yeo, I., Farquharson, C., Petersen, S., and Evans,R. (2021). Magnetic and gravity surface geometry inverse modeling of the TAG active mound. Journal of Geophysical Research: Solid Earth, 126, e2021JB022228. https://doi.org/10.1029/2021JB022228. Citation added for users reference in metadata descriptions. https://doi.org/10.1029/2021JB022228 The noise levels for the final processed total magnetic intensity were determined to have a mean of 0.0 and a standard deviation of 8 percent (assuming Gaussian noise). This value was determined during the inversion modelling process, where multiple models were produced with varying data misfit targets (such as, the difference between the observed data and the final inversion model's calculated data), until a model was produced with minimal-to-no near-seafloor, small (single cell sized), high magnetic susceptibility artifacts interpreted to represent overfitting the data. This 8 percent standard deviation noise is likely so high because it incorporates positional inaccuracy of the survey platform (the AUV Sentry), see Galley and others (2021) in the Supplementary Material of the publication for details. The data does match with details provided about it, and all data falls within expected ranges. No duplicates are present in the files. Total magnetic intensity data is geographically dependent, such as, values can change greatly depending on where the survey took place. This data only represents total magnetic intensity data within the corresponding survey areas, in the spring of 2022. Sentry’s internal navigation is dead reckoning based on the Inertial Navigation System (INS) and Doppler Velocity Log (DVL) sonar system. It has a typical accuracy of 0.1 percent of distance traveled. The Sentry dives at the Escanaba Trough were between 24-51 km in survey distance travelled, corresponding to positional accuracies of 24-51 m by the end of the surveys. However, post-processing can greatly increase the accuracy of the positional data. A better estimate of the horizontal accuracy of the Sentry AUV would be 6-8 m, as determined through testing in Galley and others (2021). Sentry's depth information is much more accurate than the horizontal positional data, as it is determined through pressure measurements (using a Parascientific 8B7000-1m Digiquartz depth sensor). The depth sensor boasts a 0.01 percent accuracy, so the average survey depth at the Escanaba Trough of approximately 3.2 km would correspond to a survey depth data accuracy of approximately 32 cm. Magnetics data was collected by a three-component fluxgate magnetometer attached the autonomous underwater vehicle (AUV) Sentry during the TN403 expedition in the Escanaba Trough on the R/V Thomas G. Thompson. The expedition occurred between May 24, 2022, and June 13, 2022, and was led and staffed by USGS employees. 20220613 Magnetics data were compiled and cleaned upon returning to land. To remove the magnetization effects from the AUV, a full-vector calibration was performed, which involved spinning the AUV in the water column to complete at least one 360-degree rotation. The attitude and vector magnetic field data from these rotations were used to calculate the induced and permanent magnetization of the AUV using a least-squares solution and subsequently removed from the raw data. The resulting files from this initial calibration are, which also include raw data columns: escanaba_d638_mag.csv; escanaba_d639_mag.csv; escanaba_d640_mag.csv; escanaba_d641_mag.csv; escanaba_d642_mag.csv; escanaba_d643_mag.csv; escanaba_d646_mag.csv; escanaba_d647_mag.csv. The calibration matrices used in the full-vector calibration are included in the file Calibration_Coefficient_Matrices.txt. To further prepare the vector magnetic data for the inversion modelling the data were: (1) low-pass filtered with a passband frequency of 0.01 Hz at a data frequency of 10 Hz; (2) projected to WGS 1984 UTM Zone 9N; (3) separated into single survey lines with the ends of the lines where the AUV turned around removed, each line was levelled to its survey's tie line(s); (4) further linear heading corrections were calculated and applied to each individual survey line, to remove artifacts left over from the full-vector calibration; (5) a 50 m moving mean was applied to the data along each survey line, and then the data was subsampled to a 50 m data point spacing; (6) the survey lines were combined into new survey groups, with dive 643's data being separated into two surveys, d643_1 and d643_23, and dive 638, 640, and 641 were combined into a single group; and (7) the Earth's field strength was calculated at each survey location using the WMM-2020 model (https://www.ngdc.noaa.gov/geomag/calculators/magcalc.shtml#igrfwmm), and was subtracted from the data to produce a TMI anomaly. The resulting data files are: d638_mag_lvled_50m_UTM9N.csv; d639_mag_lvled_50m_UTM9N.csv; d640_mag_lvled_50m_UTM9N.csv; d641_mag_lvled_50m_UTM9N.csv; d642_mag_lvled_50m_UTM9N.csv; d646_mag_lvled_50m_UTM9N.csv; d647_mag_lvled_50m_UTM9N.csv. 20260123 Vector data of the X, Y, and Z directions of the magnetic field were during each of AUV Sentry's dive while the magnetometer was attached. 0.0000001 0.0000001 Decimal degrees World Geodetic System 1984 (WGS 84) WGS_1984 6378137.0 298.257223563 mean sea level 0.1 0.1 meters Explicit elevation coordinate included with horizontal coordinates escanaba_dXXX_mag.csv Comma Separated Value (CSV) file containing raw magnetics data. The XXX in the file name represents the dive number. For example, escanaba_d638_mag.csv contains data from dive 638. Producer Defined Year The year component of the data's timestamp Producer Defined 2022 2022 years Month The month component of the data's timestamp Producer Defined 5 6 months Day The day component of the data's timestamp Producer Defined 1 31 days Hour The hour component of the data's timestamp Producer Defined 0 23 hours Minute The minute component of the data's timestamp Producer Defined 0 59 minutes Second The second component of the data's timestamp Producer Defined 0 60 seconds Longitude_DD Longitudinal data formatted in decimal degrees Producer Defined -127.5671398 -127.4023971 decimal degrees Latitude_DD Latitudinal data formatted in decimal degrees Producer Defined 40.6942229 41.1735022 decimal degrees Elevation_m Elevation data of the observation points relative to sea-level, units in meters (m) Producer Defined -3273.01 -3086.87 meters Altitude_m Altitude data formatted in meters. This represents the relative height of the observation points above the seafloor Producer Defined 49.34 127.37 meters Heading Heading data of the AUV Producer Defined 0.0 360.0 degrees Pitch Pitch data of the AUV Producer Defined -11.85 11.301 degrees Roll Pitch data of the AUV Producer Defined -3.379 6.815 degrees Mag_x_raw_nT The x-component (North positive) of the raw magnetic field data. Units in nano tesla (nT) Producer Defined -29991.87 28199.46 nano tesla Mag_y_raw_nT The y-component (East positive) of the raw magnetic field data. Units in nano tesla (nT) Producer Defined -25141.69 24708.65 nano tesla Mag_z_raw_nT The x-component (North positive) of the raw magnetic field data. Units in nano tesla (nT) Producer Defined 38935.41 49413.95 nano tesla TMI_raw_nT The total magnetic intensity raw data. Units in nano tesla (nT) Producer Defined 43661.5 51478.94 nano tesla Mag_x_veccorr_nT The x-component (North positive) of the vector-corrected magnetic field data. Units in nano tesla (nT) Producer Defined 19060.95 23426.19 nano tesla Mag_y_veccorr_nT The y-component (East positive) of the vector-corrected magnetic field data. Units in nano tesla (nT) Producer Defined 2767.21 8150.08 nano tesla Mag_z_veccorr_nT The z-component (vertical, down positive) of the vector-corrected magnetic field data. Units in nano tesla (nT) Producer Defined 37052.03 45919.48 nano tesla TMI_veccorr_nT The total magnetic intensity vector-corrected data. Units in nano tesla (nT) Producer Defined 42218.74 51085.81 nano tesla dXXX_mag_lvled_50m_UTM9N.csv Comma Separated Value (CSV) file containing processed magnetics data. The XXX in the file name represents the dive number. For example, d638_mag_lvled_50m_UTM9N.csv contains data from dive 368. Producer Defined Easting_m Easting positional data, in the WGS 1984 UTM Zone 9 projection. Units in meters (m) Producer Defined 620722.4 633887.4 meters Northing_m Northing positional data, in the WGS 1984 UTM Zone 9 projection. Units in meters (m) Producer Defined 4505892.6 4559228.9 meters Elevation_m Elevation data of the observation points relative to sea-level, units in meters (m) Producer Defined -3272.8 -3087.0 meters Altitude_m Altitude data formatted in meters. This represents the relative height of the observation points above the seafloor Producer Defined 63.7 91.7 meters TMI_Anomaly_nT The total magnetic intensity anomaly data, units in nano tesla (nT) Producer Defined -415.9 2597.6 nano tesla This dataset consists of data from eight marine magnetic field surveys collected down the length of the Escanaba Trough in the northeast Pacific Ocean. The data were measured with a three-component fluxgate magnetometer, mounted to Woods Hole Oceanographic Institute's autonomous underwater vehicle Sentry. Included in this dataset are the eight survey's calibrated vector (three-component) magnetic data, as well as the processed versions of the data presented as total magnetic intensity. 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 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. comma-delimited text 2025a These data are available in comma-delimited text format accompanied by the associated CSDGM FGDC-compliant metadata. Files are provided in two zip folders as the final data (final_data_used_in_modeling) and the vector corrected data (vector_corrected). No compression applied. 146.5 https://doi.org/10.5066/P1DRPIQK Data and metadata can be downloaded using the Network_Resource_Name link and scrolling down to the Magnetic Data section. None These data can be viewed with any text reader. 20260401 PCMSC Science Data Coordinator U.S. Geological Survey, Pacific Coastal and Marine Science Center mailing

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