Travis Alongi Alicia F. Balster-Gee Jared W. Kluesner Ray W. Sliter 20230809 seismic-reflection data in SEG-Y format data release DOI:10.5066/P9FOES4K Pacific Coastal and Marine Science Center, Santa Cruz, California U.S. Geological Survey Suggested Citation: Alongi, T., Balster-Gee, A.F., Kluesner, J.W., Sliter, R.W., 2023, Reprocessed multichannel seismic reflection data acquired offshore Southern California during USGS field activity L-4-90-SC: U.S. Geological Survey data release, https://doi.org/10.5066/P9FOES4K. https://doi.org/10.5066/P9FOES4K Multichannel seismic (MCS) data were collected by the U.S. Geological Survey (USGS) in 1990 in the California Continental Borderland (USGS field activity L490SC). In 2021 these data were reprocessed to improve accuracy and resolvability of geologic structures and fault systems of California’s continental margin. MCS data were acquired to support the Southern California Earthquake Hazards project to help mitigate earthquake and tsunami hazards for the Southern California region by improving our understanding of how deformation is distributed (spatially and temporally) in the offshore with respect to the onshore region. The reprocessed dataset enhances the seismic data quality which will be useful for future research on the geomorphic, sedimentary and tectonic history offshore California. These data are intended for science researchers, students, policy makers, and the general public. 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=L490SC 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. 19900509 19900525 ground condition at time data were collected Complete None planned -121.090570 -117.387666 31.190785 35.321160 USGS Metadata Identifier USGS:dcb63f18-fef7-44af-8e36-da9b6b195c45 ISO 19115 Topic Category oceans geoscientificInformation location Data Categories for Marine Planning substrate USGS Thesaurus marine geophysics sub-bottom profiling geospatial datasets Marine Realms Information Bank (MRIB) keywords data processing seismic reflection profiling Global Positioning System (GPS) observations None U.S. Geological Survey USGS Coastal and Marine Hazards and Resources Program CMHRP Pacific Coastal and Marine Science Center PCMSC shapefile seismic navigation seismic reflection sub-bottom profiling SEG-Y traces R/V Ocean Olympic Geographic Names Information System (GNIS) Pacific Ocean State of California Santa Monica Bay San Pedro Bay San Pedro Channel Gulf of Santa Catalina Santa Catalina Island Torrance Long Beach Huntington Beach Newport Beach Laguna Beach Dana Point San Clemente Oceanside Carlsbad Encinitas Solana Beach San Diego Coronado Imperial Beach Avalon NGA GEOnet Names Server (GNS) Redondo Canyon San Pedro Escarpment San Pedro Basin Lasuen Knoll Carlsbad Canyon La Jolla Canyon Coronado Canyon San Diego Trough San Nicolas Basin Emery Basin San Clemente Basin East Cortes Basin Cortes Bank Tanner Bank Tanner Basin Santa Cruz Basin Arguello Terrace Santa Lucia Bank None Point Loma 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 831-427-4747 pcmsc_data@usgs.gov L490SC.preview.png Map of MCS tracklines acquired during USGS field activity L-4-90-SC offshore Southern California. PNG Reprocessing efforts were supported by an Interagency Agreement (IAA) between the Bureau of Ocean Energy Management (BOEM) and the U.S. Geological Survey. The authors acknowledge Danny Brothers (USGS) and Mark Leung (BOEM) for their role in coordinating the IAA. The authors also acknowledge the participants of the field activity L-4-90-SC, the crew of the R/V S.P. Lee and those involved in in survey planning and execution. SEG-Y reprocessing was conducted in Shearwater’s Reveal seismic software (https://www.shearwatergeo.com/4/reveal-software) version 10.4.2021. Navigation correction used the python package segyio (https://github.com/equinor/segyio). QGIS-LTR (version 3.21, https://www.qgis.org/en/site/) was used to produce the navigation trackline shapefile and preview image. R.G. Bohannon S.L. Eittreim J.R. Childs 1999 Bohannon, R.G., Eittreim, S.L., and Childs, J.R., 1990, Cruise Report of R/V S.P. Lee, Leg 4, 1990, California continental borderland: U.S. Geological Survey Open-File Report 90-0502, 10 p., http://pubs.usgs.gov/of/1990/0502/report.pdf. http://pubs.usgs.gov/of/1990/0502/report.pdf Michael A. Fisher Victoria E. Langenheim Craig Nicholson Holly F. Ryan Ray W. Sliter 2000 Fisher, M.A., Langenheim, V.E., Nicholson, C., Ryan, H.F., and Sliter, R.W., 2009, Recent developments in understanding the tectonic evolution of the Southern California offshore area: Implications for earthquake-hazard analysis, in Lee, H.J., and Normark, W.R., (eds.) Earth Science in the Urban Ocean: The Southern California Continental Borderland: Geological Society of America Special Papers, v. 454, https://doi.org/10.1130/2009.2454(4.2). Quality control was conducted during acquisition. Some seismic profiles have gaps in them due to system crashes or intentional shutdowns as required, under terms of our operating permit, to protect marine mammals. Quality control was conducted during acquisition and processing to ensure consistency of SEG-Y header navigation and seismic-reflection data that matches bathymetry along the tracklines. Navigation data are available as a trackline shapefile in the ‘Data Files’ section. Trackline navigation combines SEG-Y line parts into a single-track line (32 tracklines and 32 SEG-Y files, including parts). 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. Seismic data are unavailable where equipment failed and where marine mammal observers determined mammals were within the 250-m shutdown radius. The primary underway navigational sensor was Loran-C operated in the range-range mode. Loran-C calibration factors were derived from GPS solutions when GPS coverage was adequate(approximately 12 hours per day). The absolute accuracy of LORAN-C varies from 0.10 to 0.25 nmi (185 to 463 m). Repeatable accuracy is much greater, typically from 60 to 300 ft (18 to 91 m) (COMDTPUB P16562.6, "LORAN-C Users Handbook", 1992, https://chetaero.files.wordpress.com/2016/11/loran-c_users_handbook_entire.pdf). Further positional error may have been introduced from assigning receiver locations and CMP binning. P.E. Hart 2016 SEG-Y online U.S. Geological Survey https://walrus.wr.usgs.gov/namss/survey/l-4-90-sc/ online database 19900509 19900525 ground condition at time data were collected original seismic-reflection data seismic shot SEG-Y data for reprocessing Multichannel seismic-reflection data were acquired with a 10-airgun array seismic source with a combined chamber volume of 2424 cubic inches. The data were recorded using a 48-channel analog streamer which were spaced at 50 meter intervals, the furthest offsets was 2.4 kilometers aft of the airgun array. The length of the streamer and the 50 meter shot interval results in a fold of 20 traces or greater. The seismic traces were recorded at 2 ms sample rate with a total record length of 12 seconds. original seismic-reflection data 19920520 Raw pre-stack SEG-Y data was imported into Reveal seismic software (https://www.shearwatergeo.com/4/reveal-software, v. 10.4.2019), where The seismic traces were detrended and the applied tape delay was removed. Corrections were applied to the SEG-Y headers which were recorded in reverse channel order and offsets were corrected to positive values. The preceding steps were applied to perform frequency - wavenumber analysis, with which noise and aliased signal were isolated and removed in Fourier space leaving the desired reflection signal. The raw data was quality controlled and 4 noisy channels at the furthest offsets were removed. The data was despiked, cleaned and trim statics were applied. Deconvolution wass done prestack and removed the source signature from the geologic reflections in order to produce crisp, collapsed, and high-resolution imaging. The deconvolution operator is an inverse filter that is computed statistically on a per-channel basis. The detailed 2D subsurface velocity structure was determined in a semblance analysis workflow. The velocity field was used to correctly move out the data before stacking to increase resolution, suppress random noise and reduce contamination from the sea surface multiple. Post-stack time migration was applied at 85 percent of the picked velocity for this data set. Finally, the water column was muted and the bottom edge of the data were muted. Data were exported to SEG-Y format with navigation in standard header byte locations and zipped into L490SC.mcs.segy.zip. CMP navigation was converted from points to a multi-line shapefile in QGIS-LTR (v. 3.21) and zipped into L490SC.mcs.trackline.shapefile.zip. 20200520 Point Point 32 0.000001 0.000001 Decimal degrees WGS 1984 WGS 84 6378137.0 298.257224 L490SC.mcs.segy.zip Zip archive of 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 L490SC.mcs.trackline.shapefile.zip Zip file contains a polyline shapefile (.shp) of the location of each SEG-Y shot point along the navigated tracklines and associated files U.S. Geological Survey LINE Number of navigation line Assigned unique line identifier name Producer-assigned unique line identifier name Seismic Shots with Time Stamp in standard SEG-Y file format, with trackline navigation presented in polyline shapefile format. Society of Exploration Geophysicists (SEG) Technical Standards, available for download at http://seg.org/Publications/SEG-Technical-Standards U.S. Geological Survey - CMGDS mailing and physical

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Santa Cruz CA 95060 831-427-4747 pcmsc_data@usgs.gov SEG-Y data are available in the zip file L490SC.mcs.segy.zip containing 32 standard SEG-Y format files of seismic shots with time stamp (Society of Exploration Geophysicists (SEG) Technical Standards, available for download at http://seg.org/Publications/SEG-Technical-Standards). A shapefile of the SEG-Y shot-track navigation is available in the zip file L490SC.mcs.trackline.shapefile.zip. 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 (L490SC.mcs.segy.zip) contains the processed seismic data per navigation line. The zip file can be decompressed with any zip utility (for example, 7zip, Keka, WinZip). 489.1 https://doi.org/10.5066/P9FOES4K SEG-Y data (L490SC.mcs.segy.zip) can be downloaded using the Network_Resource_Name link and scrolling to the Seismic Data section. shapefile ArcGIS Pro (version 2.4.1) Zip file contains a shapefile with SEG-Y trackline navigation The zip file can be decompressed with any zip utility (for example, 7zip, Keka, WinZip). 1.2 https://doi.org/10.5066/P9FOES4K Data (L490SC.mcs.trackline.shapefile.zip) can be downloaded using the Network_Resource_Name link and scrolling to the Seismic Data section. None. Use of SEG-Y data requires specialized software, such as Reveal by Shearwater; 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. Users must have software capable of reading shapefile (.shp) format to use the shot point shapefile. 20230809 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