Daniel J. Kennedy Maureen A.L. Walton Guy R. Cochrane Charles K. Paull David W. Caress Krystle Anderson Eve Lundsten Lisa Gilbane 20210823 Chirp seismic-reflection data in SEG-Y format data release DOI:10.5066/P97QM7NF Pacific Coastal and Marine Science Center, Santa Cruz, California U.S. Geological Survey https://doi.org/10.5066/P97QM7NF Daniel J. Kennedy Maureen A.L. Walton Guy R. Cochrane Charles K. Paull David W. Caress Krystle Anderson Eve Lundsten Lisa Gilbane 2021 data release DOI:10.5066/P97QM7NF Pacific Coastal and Marine Science Center, Santa Cruz, CA U.S. Geological Survey https://doi.org/10.5066/P97QM7NF This dataset consists of autonomous underwater vehicle (AUV) Chirp seismic-reflection data collected in May 2019 aboard the R/V Rachel Carson, which is owned and operated by the Monterey Bay Aquarium Research Institute (MBARI). During the cruise, data were collected across four AUV dives, all four of which collected coincident bathymetry and Chirp seismic-reflection data. The collection of these data was funded entirely by MBARI, and the data have been donated to the U.S. Geological Survey (USGS). The data were collected in collaboration with the USGS and the Bureau of Ocean Energy Management (BOEM), and they are located in the same study area as the collaborative California Deepwater Investigations and Groundtruthing I (Cal DIG I) project. The purpose of the overall Cal DIG I study is to assess shallow geohazards, benthic habitats, and thereby the potential for alternative energy infrastructure (namely floating wind turbines) offshore south-central California due to the study area's proximity to power grid infrastructure associated with the Morro Bay power plant. The AUV data in this portion of the data release provide ultra-high-resolution subsurface imaging of four different patches of seafloor offshore of the south-central California coast. The AUV mapping navigation has not been accurately positioned and is considered as only partially processed. The goal of this part of the Cal DIG I study is to collect overlapping multibeam bathymetry and Chirp seismic-reflection data offshore of south-central region of California for the purpose of improving regional models of seafloor (benthic) habitats, sediment transport, and assessing potential geologic hazards. Additional information about the USGS field activity from which these data were derived is available online at: http://cmgds.marine.usgs.gov/2021-605-DD 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 data set in nonproprietary form, as well as in Esri format, this metadata file may include some Esri-specific terminology. 20190510 20190511 Ground conditions at time data were collected. In work As needed -121.564 -121.378 35.306 35.001 USGS Metadata Identifier USGS:82e35542-59c8-4708-9233-e286544fcee3 ISO 19115 Topic Category oceans elevation geoscientificInformation Data Categories for Marine Planning Substrate Distributions USGS Thesaurus sub-bottom profiling sea-floor characteristics geospatial datasets marine geophysics Marine Realms Information Bank (MRIB) keywords acoustic methods None U.S. Geological Survey USGS Coastal and Marine Hazards and Resources Program CMHRP Pacific Coastal and Marine Science Center PCMSC Monterey Bay Aquarium Research Institute MBARI Edgetech 2205 1-6 kHz AUV Chirp sub reflection profiling Geographic Names Information System (GNIS) Pacific Ocean State of California Morro Bay NGA GEOnet Names Server (GNS) Santa Lucia Bank Santa Barbara Basin none Santa Maria Basin Diablo Canyon 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 and Monterey Bay Aquarium Research Institute (MBARI) 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 831-427-4747 pcmsc_data@usgs.gov MBARI_AUVchirp_May2019_thumbnail.png Bathymetry map offshore of south-central California overlaid with MBARI-donated AUV survey data in blue. PNG The donated data was collected aboard the R/V Rachel Carson, which is owned and operated by the Monterey Bay Aquarium Research Insitute. SEG-Y Rev 1 The AUV system developed at MBARI has an estimated vertical depth uncertainty ranging from about 0.05 m to 2.0 m over a horizontal range of 0 to 5 m. Accuracies of final products may be lower due to total propagated uncertainties of the mapping systems, which include sonar system, position and motion compensation system, and navigation, as well as data processing that includes sounding cleaning and datum transformations. The subbottom data are collected from a submerged platform for which both the vertical position and the altitude over the seafloor are variable. In any time section or depth section, the data must start at the location of the sonar in time or depth, not at the top of the plot. The trace is recorded in TWTT (seconds), but the sonar depth is recorded to the headers (49-52, 61-64, and 65-68) in meters – so the sonar depth needs to be converted to TWTT seconds in order to be added to the Chirp trace to correct for water depth. No formal logical accuracy tests were conducted. Dataset is considered partially complete for the information presented. AUV mapping data have not had the navigation corrected. Users are advised to read the rest of the metadata record carefully for additional details. Position data derive from an onboard inertial navigation system (INS) that has drift bounded by 0.05 percent of distance traveled when aided by Doppler Velocity Log (DVL) velocity over ground observations. The raw INS positions are adjusted in post processing so that bathymetric features match in overlapping swath data. Following the navigation adjustment relative position accuracy within the surveys is less than 2 m. The absolute position accuracy is dominated by Ultra Short Base Line (USBL) tracking of the AUV at the beginning of missions, which is less than 30 m. Bottom positions were modified using MBSystem NavAdjust to make bathymetric features in overlapping swaths and crossing swath match. Data have not been adjusted to match surface ship collected multibeam bathymetry. Depths shown in the seismic-reflection data files are in milliseconds (round trip travel time) and are referenced to sea level. Vertical accuracy ranges between +/- 0.2 and 1 meter. Detailed seafloor surveys were conducted using an AUV developed at the Monterey Bay Aquarium Research Institute (MBARI) specifically for seafloor mapping. The vehicle carried a Reson 7125 400kHz multibeam sonar and an Edgetech 2205 1-6 kHz subbottom profiler. The AUV was preprogrammed to proceed to more than 50 waypoints during the dives while traveling at 3 knots and maintaining an altitude of 50 m off the seafloor. Track lines were spaced 140-150 m apart. In this mode, the AUV obtains overlapping multibeam bathymetric coverage at a vertical resolution of 0.15 m and a horizontal footprint of 0.87 m, and Chirp seismic-reflection profiles with a vertical resolution of 0.11 m. 20190511 Performed minor edits to the metadata to correct typos. No data were changed 20211013 U.S. Geological Survey Susan A. Cochran Geologist Mailing and Physical

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Santa Cruz CA 95060 831-460-7545 scochran@usgs.gov Data were collected offshore of south-central California. SEG-Y file headers contain location information. WGS 1984 UTM Zone 10N 0.9996 -121.5 0.0 500000.0 0.0 coordinate pair 0.0001 0.0001 Meter World Geodetic System 1984. WGS 1984 6378137.0 298.257223563 North American Vertical Datum 1988 (NAVD-88) 0.01 meters Explicit elevation coordinate included with horizontal coordinates value depth in meters relative to NAVD-88 Producer defined The partially complete AUV Chirp was originally achieved as a collection of 0.5-2.0 m resolution seismic profiles recorded in SEG-Y format. U.S. Geological Survey U.S. Geological Survey mailing and physical

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Santa Cruz CA 95060 831-427-474 pcmsc_data@usgs.gov Zip files contain partially processed AUV Chirp seismic-reflection data in zipped SEG-Y format. The data are divided up into folders by dive and presented by navigation line, as reflected in the individual file name(s). Download sizes range from 1.7 to 2.4 GB. 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 files contain the partially processed AUV Chirp seismic-reflection data divided into folders by dive with individual files per navigation line. Download sizes range from 1.7 to 2.4 GB. Winzip, 7-zip, or Winrar are free software that will open .zip files. 2400 https://doi.org/10.5066/P97QM7NF Data and metadata can be downloaded using the Network_Resource_Name link and scrolling down to the Seismic Data section. None. The downloadable data file has been compressed with the "zip" command and can be unzipped with Winzip (or other tool) on Windows systems. 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. 20211013 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