Reprocessed legacy seismic-reflection data from USGS field activity B-1-72-SC collected offshore southern California
Seismic-reflection data were collected offshore southern California in 1972 aboard the USNS Bartlett (USGS Field Activity B-1-72-SC). In 2021 these legacy data were reprocessed to improve accuracy and geologic resolvability of California’s continental margin.
Kennedy, Daniel J., Balster-Gee, Alicia F., Sliter, Ray W., and Kluesner, Jared W., 20220428, Reprocessed legacy seismic-reflection data from USGS field activity B-1-72-SC collected offshore southern California: data release DOI:10.5066/P9EK7CG3, U.S. Geological Survey, Pacific Coastal and Marine Science Center, Santa Cruz, California.
Kennedy, Daniel J., Balster-Gee, Alicia F., Sliter, Ray W., and Kluesner, Jared W., 2022, Reprocessed legacy seismic-reflection data from USGS field activity B-1-72-SC collected offshore central and southern California: data release DOI:10.5066/P9EK7CG3, U.S. Geological Survey, Pacific Coastal and Marine Science Center, Santa Cruz, CA.
Planar coordinates are encoded using coordinate pair
Abscissae (x-coordinates) are specified to the nearest 0.0001
Ordinates (y-coordinates) are specified to the nearest 0.0001
Planar coordinates are specified in Meter
The horizontal datum used is D_WGS_1984.
The ellipsoid used is WGS_1984.
The semi-major axis of the ellipsoid used is 6378137.0.
The flattening of the ellipsoid used is 1/298.257223563.
Data were acquired to map geologic structure of central and southern California’s continental margin. The reprocessed dataset increases positional accuracy and enhances the data quality which will be useful for future research on the geomorphic, sedimentary and tectonic record offshore California. These data are intended for science researchers, students, policy makers, and the general public.
Original seismic-reflection data were acquired during a November 1972 cruise on the USNS Bartlett offshore of central and southern California. Profiles were collected using a sparker sound source powered between 120 and 160 kJ and recorded using an analog hydrophone streamer with navigation fixes taken at 30- to 60-minute intervals using a LORAN navigation system. Data were written to paper rolls.
Date: 17-Aug-2011 (process 2 of 4)
Scanned copies of the original paper rolls were scanned to tiff and jpeg digital format. These images have subsequently been made available in the National Archive of Marine Seismic Surveys (NAMSS; Triezenburg and others 2016).
Date: 10-Mar-2021 (process 3 of 4)
Tiff image line parts were cropped, straightened, transposed, and merged by navigation line using Adobe Photoshop. Using Image2segy software (https://gma.icm.csic.es/ca/image2segy), raster seismic images were transformed to geo-referenced SEG-Y profiles using the original 30– to 60-minute navigation fixes. Assuming a survey speed of 8 knots (4 meters per second), shots were interpolated every 1.5 seconds resulting in 6-meter spacing between successive shots. Record delays were written to SEG-Y headers.
Date: 10-Mar-2022 (process 4 of 4)
The following process steps were applied using Shearwater’s Reveal seismic software (https://www.shearwatergeo.com/4/reveal-software): delay recording time shift, water column mute, bottom mute 2700 ms below the water bottom, time migration at a constant 1600m/s, 3 trace median gather filter, 0-10-150-200 Hz Bandpass filter, and a final water column mute and bottom mute.
Triezenberg, Peter J., Hart, Patrick E., and Childs, Jonathan R., 2016, National Archive of Marine Seismic Surveys (NAMSS): A USGS data website of marine seismic reflection data within the U.S. Exclusive Economic Zone (EEZ).
Triezenberg, P.J., Hart, P.E., and Childs, J.R., 2016, National Archive of Marine Seismic Surveys (NAMSS): A USGS data website of marine seismic reflection data within the U.S. Exclusive Economic Zone (EEZ): U.S. Geological Survey data release, https://doi.org/10.5066/F7930R7P.
Greene, H. Gary, Silver, Eli A., and Roland E. von Huene, 1975, Seismic reflection profiles November 1972 cruise, USNS Bartlett, offshore Central and southern California.
How well have the observations been checked?
Scanned copies of the original seismic-reflection data from paper rolls were provided by PG&E for this project. As these are scanned copies, an unknown loss of resolution may have occurred. These scanned copies of the original paper records are identified as the best available version and from which modern (c. 2021-2022) reprocessing of this legacy data occurred.
How accurate are the geographic locations?
Navigation fixes are only every 30 minutes to 1 hour using a LORAN navigation system that has a horizontal accuracy within tens of miles. Reprocessed data interpolates position for each trace using the original navigation fixes.
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.
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.
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.