Metadata: Identification_Information: Citation: Citation_Information: Originator: Janet T. Watt Originator: Victoria E. Langenheim Originator: Lydia M. Staisch Publication_Date: 20250403 Title: Detailed aeromagnetic survey grid of the Trinidad Area, California Geospatial_Data_Presentation_Form: raster digital data Series_Information: Series_Name: data release Issue_Identification: DOI:10.5066/P13SZBH7 Publication_Information: Publication_Place: Pacific Coastal and Marine Science Center, Santa Cruz, California Publisher: U.S. Geological Survey Online_Linkage: https://doi.org/10.5066/P13SZBH7 Larger_Work_Citation: Citation_Information: Originator: Janet T. Watt Originator: Victoria E. Langenheim Originator: Lydia M. Staisch Publication_Date: 2025 Title: Detailed Aeromagnetic Survey of the Trinidad Area, California Series_Information: Series_Name: data release Issue_Identification: DOI:10.5066/P13SZBH7 Publication_Information: Publication_Place: Pacific Coastal and Marine Science Center, Santa Cruz, California Publisher: U.S. Geological Survey Other_Citation_Details: Suggested Citation: Watt, J.T., Langenheim, V.E., and Staisch, L.M., 2025, Detailed aeromagnetic survey of the Trinidad Area, California: U.S. Geological Survey data release, https://doi.org/10.5066/P13SZBH7. Online_Linkage: https://doi.org/10.5066/P13SZBH7 Description: Abstract: This data release provides access to gridded data from a low-altitude, aeromagnetic survey of a part of northwestern California. The survey extends west of the Klamath Mountains across the Pacific Ocean coastline over the continental shelf and covers the towns of Crescent City, Trinidad, Fortuna, Eureka, Arcata, and McKinleyville. Data were acquired during the summer and fall of 2024 by Xcalibur Multiphysics working under contract to the Yurok Tribe and under supervision of the U.S. Geological Survey. Total magnetic field values were acquired using a fixed-wing aircraft flown at a target elevation of 305 meters (m) above terrain and along flight lines and tie lines spaced 600 m and 6000 m apart, respectively. Flight lines were directed northeast-southwest; tie lines were directed northwest-southeast. A total of 13,134 line-kilometers were acquired. Purpose: These data were acquired to support earthquake hazard investigations and geologic mapping of the greater Trinidad area of northwestern California. The primary focus was to map continuity and geometry of faults and folds from the town of Fortuna north to Smith River. Supplemental_Information: Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Time_Period_of_Content: Time_Period_Information: Range_of_Dates/Times: Beginning_Date: 20240828 Ending_Date: 20240927 Currentness_Reference: ground condition Status: Progress: Complete Maintenance_and_Update_Frequency: None planned Spatial_Domain: Bounding_Coordinates: West_Bounding_Coordinate: -124.5260 East_Bounding_Coordinate: -123.7210 North_Bounding_Coordinate: 41.9360 South_Bounding_Coordinate: 40.5660 Keywords: Theme: Theme_Keyword_Thesaurus: USGS Metadata Identifier Theme_Keyword: USGS:711dd816-65fa-49b0-82cc-1b63a94d350b Theme: Theme_Keyword_Thesaurus: Data Categories for Marine Planning Theme_Keyword: substrate Theme: Theme_Keyword_Thesaurus: ISO 19115 Topic Category Theme_Keyword: geoscientificInformation Theme: Theme_Keyword_Thesaurus: Marine Realms Information Bank (MRIB) Keywords Theme_Keyword: continental margin Theme_Keyword: magnetic field observations Theme: Theme_Keyword_Thesaurus: USGS Thesaurus Theme_Keyword: magnetic field (earth) Theme_Keyword: magnetometer measurement Theme_Keyword: aeromagnetic surveying Theme_Keyword: crust (earth) Theme_Keyword: neotectonic processes Theme_Keyword: earthquakes Theme: Theme_Keyword_Thesaurus: None Theme_Keyword: U.S. Geological Survey Theme_Keyword: USGS Theme_Keyword: Coastal and Marine Hazards and Resources Program Theme_Keyword: CMHRP Theme_Keyword: Pacific Coastal and Marine Science Center Theme_Keyword: PCMSC Theme_Keyword: magnetic anomaly Place: Place_Keyword_Thesaurus: Geographic Names Information System (GNIS) Place_Keyword: State of California Place_Keyword: Trinidad Place_Keyword: Fortuna Place_Keyword: McKinleyville Place_Keyword: Arcata Place_Keyword: Eureka Place_Keyword: Orick Place_Keyword: Crescent City Access_Constraints: No access constraints. Please see 'Distribution Info' for details. Use_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. Please recognize and acknowledge the U.S. Geological Survey as the originator(s) of the dataset and in products derived from these data. Users are advised to read the data set's metadata thoroughly to understand appropriate use and data limitations. Point_of_Contact: Contact_Information: Contact_Person_Primary: Contact_Person: PCMSC Science Data Coordinator Contact_Organization: U.S. Geological Survey, Pacific Coastal and Marine Science Center Contact_Address: Address_Type: mailing address Address: 2885 Mission Street City: Santa Cruz State_or_Province: CA Postal_Code: 95060 Country: US Contact_Voice_Telephone: 831-427-4747 Contact_Electronic_Mail_Address: pcmsc_data@usgs.gov Data_Set_Credit: The Trinidad aeromagnetic survey was conducted by Xcalibur Multiphysics, working under contract with the Yurok Tribe and under supervision of the U.S. Geological Survey. David Miles was project manager and data processing was done by Fabian Linares and Tonia Bojkova. The Yurok Tribe coordinated flight and access permissions. Cross_Reference: Citation_Information: Originator: Alken, P. Originator: Thébault, E. Originator: Beggan, C.D. Originator: Amit, H. Originator: Aubert, J. Originator: Baerenzung, J. Originator: Bondar, T.N. Originator: Brown, W.J. Originator: Califf, S. Originator: Chambodut, A. Originator: Chulliat, A. Originator: Cox, G.A. Originator: Finlay, C.C. Originator: Fournier, A. Originator: Gillet, N. Originator: Grayver, A. Originator: Hammer, M.D. Originator: Holschneider, M. Originator: Huder, L. Originator: Hulot, G. Originator: Jager, T. Originator: Kloss, C. Originator: Korte, M. Originator: Kuang, W. Originator: Kuvshinov, A. Originator: Langlais, B. Originator: Léger, J.-M. Originator: Lesur, V. Originator: Livermore, P.W. Originator: Lowes, F.J. Originator: Macmillan, S. Originator: Magnes, W. Originator: Mandea, M. Originator: Marsal, S. Originator: Matzka, J. Originator: Metman, M.C. Originator: Minami, T. Originator: Morschhauser, A. Originator: Mound, J.E. Originator: Nair, M. Originator: Nakano, S. Originator: Olsen, N. Originator: Pavón-Carrasco, F.J. Originator: Petrov, V.G. Originator: Ropp, G. Originator: Rother, M. Originator: Sabaka, T.J. Originator: Sanchez, S. Originator: Saturnino, D. Originator: Schnepf, N.R. Originator: Shen, X. Originator: Stolle, C. Originator: Tangborn, A. Originator: Tøffner-Clausen, L. Originator: Toh, H. Originator: Torta, J.M. Originator: Varner, J. Originator: Vervelidou, F. Originator: Vigneron, P. Originator: Wardinski, I. Originator: Wicht, J. Originator: Woods, A. Originator: Yang, Y. Originator: Zeren, Z. Originator: Zhou, B. Publication_Date: 2021 Title: International Geomagnetic Reference Field: the thirteenth generation Other_Citation_Details: Alken, P., Thébault, E., Beggan, C. D., Amit, H., Aubert, J., Baerenzung, J., Bondar, T. N., Brown, W. J., Califf, S., Chambodut, A., Chulliat, A., Cox, G. A., Finlay, C. C., Fournier, A., Gillet, N., Grayver, A., Hammer, M. D., Holschneider, M., Huder, L., Hulot, G., Jager, T., Kloss, C., Korte, M., Kuang, W., Kuvshinov, A., Langlais, B., Léger, J.-M., Lesur, V., Livermore, P. W., Lowes, F. J., Macmillan, S., Magnes, W., Mandea, M., Marsal, S., Matzka, J., Metman, M. C., Minami, T., Morschhauser, A., Mound, J. E., Nair, M., Nakano, S., Olsen, N., Pavón-Carrasco, F. J., Petrov, V. G., Ropp, G., Rother, M., Sabaka, T. J., Sanchez, S., Saturnino, D., Schnepf, N. R., Shen, X., Stolle, C., Tangborn, A., Tøffner-Clausen, L., Toh, H., Torta, J. M., Varner, J., Vervelidou, F., Vigneron, P., Wardinski, I., Wicht, J., Woods, A., Yang, Y., Zeren, Z., and Zhou, B., 2021, International Geomagnetic Reference Field: the thirteenth generation: Earth, Planets and Space, v. 73, n. 49, https://doi.org/10.1186/s40623-020-01288-x Online_Linkage: https://doi.org/10.1186/s40623-020-01288-x Data_Quality_Information: Attribute_Accuracy: Attribute_Accuracy_Report: Magnetic field values were measured with a Scintrex CS-3 cesium-vapor magnetometer, with a resolution of 0.002 nanotesla (nT). Total magnetic field values were measured at 0.05-sec intervals. Magnetic signals caused by aircraft motion and heading were compensated using a Billingsley TMF 100 Triaxial (X,Y,Z) fluxgate magnetometer mounted in the tail stinger. Prior to the survey, the aircraft and its instrumentation were put through a series of roll, pitch, and yaw maneuvers to form a model of the aircraft's magnetic characteristics. These maneuvers were performed in a region of low magnetic gradient and high altitude to minimize influence of magnetic geologic sources and to develop a compensation correction for the survey data. Two stationary magnetometers were deployed within the survey area at McKinleyville to monitor and subsequently correct for diurnal magnetic field and magnetic storm variations. The base magnetometers were GEM Systems magnetometers sampled at 1-sec intervals. Navigation was accomplished with a GPS system mounted on the tail of the aircraft. The NovAtel Model OEMV-2 receiver has a real-time accuracy of 1.5 meters (L1), sampled at 0.5-sec intervals. Logical_Consistency_Report: This dataset is considered complete for the information presented, as described in the abstract. Users are advised to read the rest of the metadata record carefully for additional details. Completeness_Report: This data set is considered complete for the information presented, as described in the abstract. Users are advised to read the rest of the metadata record carefully for additional details. Positional_Accuracy: Horizontal_Positional_Accuracy: Horizontal_Positional_Accuracy_Report: Three-dimensional positions were determined with ta NovAtel OEMV-2 receiver with an antenna mounted on the tail of the aircraft. Realtime accuracy is estimated to be 1.5 m. Vertical_Positional_Accuracy: Vertical_Positional_Accuracy_Report: Altitude was determined with the same GPS systems and a Bendix King KRA 10 radar altimeter. Altitude accuracy is estimated to be within 2 to 3 m. Lineage: Source_Information: Source_Citation: Citation_Information: Originator: Janet T. Watt Originator: Victoria E. Langenheim Originator: Lydia M. Staisch Publication_Date: 2025 Title: Detailed aeromagnetic survey point data of the Trinidad Area, California Geospatial_Data_Presentation_Form: comma-delimited text Publication_Information: Publication_Place: online Publisher: U.S. Geological Survey Online_Linkage: https://doi.org/10.5066/P13SZBH7 Type_of_Source_Media: online database Source_Time_Period_of_Content: Time_Period_Information: Range_of_Dates/Times: Beginning_Date: 20240828 Ending_Date: 20240927 Source_Currentness_Reference: ground condition Source_Citation_Abbreviation: aeromag Source_Contribution: Database of aeromagnetic point measurements along each flight line and tie line in comma-separated-value (CSV) format, available in this same data release. Process_Step: Process_Description: While in the field, the base-station magnetometers located in McKinleyville were monitored for magnetic field variations in excess of contract specifications. In the airborne magnetics, a fourth difference was calculated on the compensated total magnetic field in order to verify noise level and identify and remove discrete spikes. Data were corrected for the lag in time between the onboard GPS system and the tail-mounted magnetometer. Uncompensated and compensated total magnetic field profiles were monitored on a daily basis to assess compensation effectiveness. Readings from the two base stations were used to calculate and remove diurnal variations. Please see contractor report (2400075_YurokTribe_Tech_Report_508.pdf) in the aeromagnetic survey point dataset from this same data release for additional details. Process_Date: 20241101 Process_Contact: Contact_Information: Contact_Person_Primary: Contact_Person: Janet T. Watt Contact_Organization: U.S. Geological Survey, Pacific Coastal and Marine Science Center Contact_Position: Research Geophysicist Contact_Address: Address_Type: mailing address Address: 2885 Mission Street City: Santa Cruz State_or_Province: CA Postal_Code: 95060 Country: US Contact_Voice_Telephone: 831-460-7565 Contact_Electronic_Mail_Address: jwatt@usgs.gov Process_Step: Process_Description: Flight and tie lines were "levelled" using the statistical distribution of total field differences at each flight-line-tie-line crossing. The goal was to obtain the smoothest possible correction model for each line that minimizes the difference in magnetic field measured at each tie-line-flight-line crossing. Finally, the full International Geomagnetic Reference Field (IGRF, Alken and others, 2021), updated to the date of the survey, was subtracted from the measured, corrected total magnetic intensity, thus providing the residual magnetic intensity. The entire dataset is available in this data release in the file Trinidad_aeromag.csv. Process_Date: 20241101 Process_Step: Process_Description: Residual magnetic intensity values (channel mag_rmi in database) were interpolated to a rectilinear grid using a minimum curvature algorithm (Oasis Montaj, Geosoft). The grid is a UTM Zone 10N projection with a cell spacing of 120 by 120 m. Please see the document 2400075_YurokTribe_Tech_Report_508.pdf, in the Supplemental Files section of the point dataset from this same data release for further information. The residual magnetic intensity grid can be downloaded from this data release as a GeoTIFF contained in the file Trinidad_RMI_Final.zip. Process_Date: 20250311 Spatial_Data_Organization_Information: Direct_Spatial_Reference_Method: Raster Raster_Object_Information: Raster_Object_Type: Grid Cell Row_Count: 1266 Column_Count: 576 Spatial_Reference_Information: Horizontal_Coordinate_System_Definition: Planar: Grid_Coordinate_System: Grid_Coordinate_System_Name: Universal Transverse Mercator Universal_Transverse_Mercator: UTM_Zone_Number: 10N Transverse_Mercator: Scale_Factor_at_Central_Meridian: 0.99960000 Longitude_of_Central_Meridian: -123.00000000 Latitude_of_Projection_Origin: 0.0 False_Easting: 500000.0 False_Northing: 0.0 Planar_Coordinate_Information: Planar_Coordinate_Encoding_Method: coordinate pair Coordinate_Representation: Abscissa_Resolution: 0.0001 Ordinate_Resolution: 0.0001 Planar_Distance_Units: Meter Geodetic_Model: Horizontal_Datum_Name: World Geodetic System 1984 Ellipsoid_Name: World Geodetic System 1984 Semi-major_Axis: 6378137.0 Denominator_of_Flattening_Ratio: 298.257222101 Vertical_Coordinate_System_Definition: Altitude_System_Definition: Altitude_Datum_Name: World Geodetic System 1984 Altitude_Resolution: 5.0 Altitude_Distance_Units: meters Altitude_Encoding_Method: Explicit elevation coordinate included with horizontal coordinates Entity_and_Attribute_Information: Detailed_Description: Entity_Type: Entity_Type_Label: Trinidad_RMI_Final.tif Entity_Type_Definition: Raster geospatial data file containing gridded residual magnetic intensity values Entity_Type_Definition_Source: Producer defined Attribute: Attribute_Label: Value Attribute_Definition: Residual magnetic intensity value (gridded at 120 m interval, UTM10). Values of -3.4028234663852886e+38 indicate no data. Attribute_Definition_Source: Producer defined Attribute_Domain_Values: Enumerated_Domain: Enumerated_Domain_Value: -3.4028234663852886e+38 Enumerated_Domain_Value_Definition: no data value Enumerated_Domain_Value_Definition_Source: Producer defined Attribute_Domain_Values: Range_Domain: Range_Domain_Minimum: -410.026 Range_Domain_Maximum: 1329.842 Attribute_Units_of_Measure: nanotesla Overview_Description: Entity_and_Attribute_Overview: The data in this release are as provided to the USGS by the contractor, Xcalibur Multiphysics. The georeferenced GeoTIFF contained in Trinidad_RMI_Final.zip provides residual magnetic intensity values interpolated to a rectilinear grid. The grid is projected to Universal Transverse Mercator Zone 10N, geodetic datum WGS 84, meters. Grid spacing is 120 m in both x and y directions. Additional information is available in the accompanying document 2400075_YurokTribe_Tech_Report_508.pdf, available in the aeromagnetic survey point dataset from this same data release. Entity_and_Attribute_Detail_Citation: Airborne survey procedures, quality control, and data processing methods are described in the document 2400075_YurokTribe_Tech_Report_508.pdf, provided by the contractor. Gridded residual magnetic intensity values are presented in a georeferenced tiff (Trinidad_RMI_Final.zip). Distribution_Information: Distributor: Contact_Information: Contact_Organization_Primary: Contact_Organization: U.S. Geological Survey - CMGDS Contact_Address: Address_Type: mailing and physical Address: 2885 Mission Street City: Santa Cruz State_or_Province: CA Postal_Code: 95060 Contact_Voice_Telephone: 831-427-4747 Contact_Electronic_Mail_Address: pcmsc_data@usgs.gov Distribution_Liability: 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. Standard_Order_Process: Digital_Form: Digital_Transfer_Information: Format_Name: GeoTIFF Format_Version_Number: Oasis Montaj, Geosoft, 2024.1 Format_Specification: Features are GeoTIFF and are projected in UTM Zone 10N. Format_Information_Content: .zip file contains the residual magnetic intensity values File_Decompression_Technique: WinZip or archive utility Transfer_Size: 2.5 Digital_Transfer_Option: Online_Option: Computer_Contact_Information: Network_Address: Network_Resource_Name: https://doi.org/10.5066/P13SZBH7 Access_Instructions: Data and metadata can be downloaded using the Network_Resource_Name link and scrolling down to the Magnetic Data section. Fees: None Technical_Prerequisites: These data can be viewed with image viewing or spatial analysis software. Metadata_Reference_Information: Metadata_Date: 20250403 Metadata_Contact: Contact_Information: Contact_Person_Primary: Contact_Person: PCMSC Science Data Coordinator Contact_Organization: U.S. Geological Survey, Pacific Coastal and Marine Science Center Contact_Address: Address_Type: mailing address Address: 2885 Mission Street City: Santa Cruz State_or_Province: CA Postal_Code: 95060 Country: US Contact_Voice_Telephone: 831-427-4747 Contact_Electronic_Mail_Address: pcmsc_data@usgs.gov Metadata_Standard_Name: Content Standard for Digital Geospatial Metadata Metadata_Standard_Version: FGDC-STD-001-1998