Ray W. Sliter James E. Conrad Thomas D. Lorenson Antoinette G. Papesh Janet T. Watt Jonathan A. Warrick 2021 seismic-reflection data in SEG-Y format data release DOI:10.5066/P9UELSBU Pacific Coastal and Marine Science Center, Santa Cruz, California U.S. Geological Survey https://doi.org/10.5066/P9UELSBU https://cmgds.marine.usgs.gov/data-releases/datarelease/10.5066-P9UELSBU/ Ray W. Sliter James E. Conrad Thomas D. Lorenson Antoinette G. Papesh Janet T. Watt Jonathan A. Warrick 2021 data release DOI:10.5066/P9UELSBU Pacific Coastal and Marine Science Center, Santa Cruz, CA U.S. Geological Survey https://doi.org/10.5066/P9UELSBU This section of the data release contains approximately 369 line-kilometers of processed, high-resolution chirp seismic-reflection profiles that were collected aboard the R/V Snavely in 2017 on U.S. Geological Survey cruise 2017-686-FA offshore Oceanside, southern California. The along-shore and across-shore chirp profiles are oriented to assess sand and gravel resources in Federal and State waters for potential use in future beach nourishment projects along stretches of the coast where critical erosion hotspots have been identified. The chirp profiles were acquired using an Edgetech 512 Chirp sub-bottom profiling system. The U.S. Geological Survey (USGS) collected high-resolution chirp seismic-reflection profiles in 2017 offshore Oceanside, southern California. The goal of the chirp survey was to provide high-resolution imaging to characterize the surface and subsurface properties of the study area, including unconsolidated sediment thickness and subsurface sediment horizons. This cruise was funded through partnerships with the Bureau of Ocean Energy Management (BOEM) and the State of California Ocean Protection Council (OPC). 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=2017-686-FA Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. 20171017 20171031 ground condition at time data were collected Planned As needed -117.53036 -117.40898 33.29839 33.21621 USGS Metadata Identifier USGS:487fe2c1-c197-45b2-82f3-58f30d8d8c2c ISO 19115 Topic Category oceans geoscientificInformation Data Categories for Marine Planning Bathymetry and Elevation USGS Thesaurus sub-bottom profiling marine geophysics geospatial datasets Marine Realms Information Bank (MRIB) keywords seismic reflection profiling 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) Pacific Ocean State of California Oceanside San Mateo Point NGA GEOnet Names Server (GNS) North Pacific Ocean None 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 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 831-460-4747 pcmsc_data@usgs.gov https://cmgds.marine.usgs.gov/data-releases/media/2020/10.5066-P9UELSBU/1abef1575c0d4002ac7de926b66222ae/2017-686-FA_chirp_sample_map.png Map showing tracklines along which chirp seismic data were collected PNG SEG-Y Rev 1 Identified as best available version. Due to horizontal amplitude variation at the seafloor, the swell correction module output anomalous static shifts that could not be improved upon. These lines are: 2, 2L, 3, 5, 06, 7, 8, 9, 10, 13, 19, 20 and 22A. Subbottom data were collected during USGS cruise 2017-686-FA using an Edgetech 512 Chirp sub-bottom profiling system. This system consists of a source transducer and an array of receiving hydrophones housed in a 500-lb “fish” towed at a depth of several meters below the sea surface. The swept-frequency “chirp” source signal is between 500 and 4,500 Hz, and data are recorded by hydrophones located on the bottom of the fish. Quality control was conducted during the collection process. 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. Equipment malfunction or shutdowns due to mammals in the area resulted in some lines having multiple parts. Position data were provided by a Hemisphere V100 Global Positioning System using L1, C/A code and carrier phase smoothing with a stated accuracy of 60 centimeters. Depths shown in the seismic data files are in milliseconds (round trip travel time) and are referenced to sea level. The chirp seismic-reflection profiles were acquired with a swept frequency source towed at 4 to 11 meters depth below the sea surface and fired at roughly every 1 to 2 meters, depending on water depth. Data were recorded to Edgetech JSF format using Edgetech recording software. Survey speeds were approximately 4.5 knots. 20171031 Chirp seismic-reflection data were first converted from JSF to SEG-Y format. The SEG-Y files were then processed using Echos by Paradigm Geophysical. The following processing steps were applied to each line: 1)The fish depth header word was read and converted from millimeters to two-way travel time to create a fish-depth static value; 2) The fish depth static was applied to the data to correct for changing tow depth of Chirp fish; 3) an additional a Paradigm Echos smoothing module was applied to the data to correct for the motion of the sea; and 4) final processed SEG-Y was output with correct navigation written to header bytes 81 and 85 in UTM zone 11N coordinates with a scalar value of 1. The scalar value located in header byte 71 only applies to arcsecond values in headers bytes 73 and 77. These data are divided up and presented by navigation line, as reflected in the individual file names. 20171115 Horizontal X and Y locations for the seismic profile locations are provided and stored in the SEG-Y data trace headers in header bytes 81 and 85 locations with a scalar of 1. WGS 1984 UTM Zone 11N 0.9996 -117.0 0.0 500000.0 0.0 coordinate pair 0.0001 0.0001 Meter D WGS 1984 WGS 1984 6378137.0 298.257223563 Local surface 0.1 meters Attribute values Navigation and seismic shots with Time Stamp in standard SEG-Y file format Society of Exploration Geophysicists (SEG) Technical Standards, available for download at http://seg.org/Publications/SEG-Technical-Standards U.S. Geological Survey – Pacific Coastal and Marine Science Center mailing and physical

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Santa Cruz CA 95060 1-831-427-4747 pcmsc_data@usgs.gov 2017-686-FA_chirp.zip contains high-resolution seismic-reflection (SEG-Y) data collected during PCMSC field activity 2017-686-FA. These data are divided up and presented by navigation line, as reflected in the individual file names. 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. SEG-Y SEG-Y rev 1 Zip file contains the processed seismic data per navigation line Winzip, 7-zip, or Winrar are free software that will open .zip files 6900 https://cmgds.marine.usgs.gov/data-releases/media/2020/10.5066-P9UELSBU/0da47f6ca7da4eadb7a5e952d0948977/2017-686_chirp.zip https://cmgds.marine.usgs.gov/data-releases/datarelease/10.5066-P9UELSBU/dataset/9/ https://doi.org/10.5066/P9UELSBU Data can be downloaded using the Network_Resource_Name links. The first link is a direct link to download the zipped file of Chirp seismic data. The second link points to a page with both the seismic data and metadata. The third link points to a landing page for the entire data release, including other data types. None. Use of SEG-Y data requires specialized software, such as ProMax and Seisworks by Landmark Geophysical; FOCUS and SeisX by Paradigm Geophysical; SPW by Parallel Geoscience; VISTA by Seismic Image Software; SeiSee by Dalmorneftegeophysica (DMNG); amongst others. 20210317 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 Content Standard for Digital Geospatial Metadata FGDC-STD-001-1998