Chirp seismic-reflection data of field activity S-5-09-SC: San Pedro Basin, offshore southern California from 2009-07-06 to 2009-07-10
This dataset includes raw and processed, high-resolution seismic-reflection data collected in 2009 to explore a possible connection between the San Diego Trough Fault and the San Pedro Basin Fault. The survey is in the San Pedro Basin between Santa Catalina Island and San Pedro, California. The data were collected aboard the U.S. Geological Survey R/V Parke Snavely. The seismic-reflection data were acquired using an EdgeTech 512 chirp subbottom profiler. Subbottom acoustic penetration spanned tens to about 50 meters, variable by location.
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=S509SC
Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.
Sliter, Ray W., Conrad, James E., Ryan, Holly F., and Triezenberg, Peter J., 2017, Chirp seismic-reflection data of field activity S-5-09-SC: San Pedro Basin, offshore southern California from 2009-07-06 to 2009-07-10: data release DOI:10.5066/F75Q4T8F, U.S. Geological Survey, Coastal and Marine Geology Program, Pacific Coastal and Marine Science Center, Santa Cruz, CA.
Horizontal X and Y locations for the seismic profile locations are provided in ASCII position files and are stored in the SEG-Y data trace headers in the standard header locations.
What coordinate system is used to represent geographic features?
Horizontal positions are specified in geographic coordinates, that is, latitude and longitude.
Latitudes are given to the nearest 0.00001.
Longitudes are given to the nearest 0.00001.
Latitude and longitude values are specified in Decimal degrees.
The horizontal datum used is D_WGS_84.
The ellipsoid used is WGS_84.
The semi-major axis of the ellipsoid used is 6378137.0.
The flattening of the ellipsoid used is 1/298.257223563.
The U.S. Geological Survey (USGS) collected high-resolution seismic-reflection in July 2009, offshore southern California, in the San Pedro Basin between San Pedro and Santa Catalina Island. The survey was designed to image faults and folds associated with movement on the numerous faults offshore southern California, including the San Pedro Basin, San Diego Trough, and several other unnamed fault zones. These data can be used to update the USGS Quaternary fault database and in shaking hazard models developed by the Working Group for California Earthquake probabilities. This work was funded by the USGS Coastal and Marine Catastrophic Hazards Project. Data were collected aboard the USGS R/V Parke Snavely. Approximately 197 km of single-channel seismic-reflection data were acquired using a SIG 2mille minisparker [DOI:10.5066/F7F769QG]. Approximately 42 km of data were collected using an EdgeTech Chirp 512 subbottom profiler. Subbottom acoustic penetration spanned tens to about 50 meters, variable by location. This data release contains raw and processed digital SEG-Y files and ASCII navigation files of the surveyed transects. The images of bedrock, sediment deposits and tectonic structure provide geologic information that is essential to hazard assessment, regional sediment management and coastal and marine spatial planning at Federal, State and local levels, as well as to future research on the geomorphic, sedimentary, tectonic and climatic record of Southern California.
Seismic-reflection data were collected using an Edgetech 512 Chirp subbottom profiling 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 approximately between 500 and 4,500 Hz, and data are recorded by hydrophones located on the bottom of the fish. At boat speeds of 4 to 4.5 nm/hour, seismic traces were collected roughly every 1 to 2 meters. The data consist of three-channels: a raw channel, a 90-degree phase-shifted channel and an “amplitude envelop” channel created and transformed internally from the other two channels. The data were recorded in standard SEG-Y 32-bit floating-point format with Triton Subbottom Logger (SBL) software that merges seismic-reflection data with differential GPS navigation data.
Date: 2015 (process 2 of 2)
The processed seismic-reflection SEG-Y files consist of the internally transformed amplitude envelope channel corrected for the depth of the fish below the sea surface using Paradigm Geophysical Echos seismic processing software (see: http://www.pdgm.com/products/echos/):
1) SEG-Y channel with sequence number “1” was written to a SEG-Y file;
2) The fish depth header word was read and converted from millimeters to two-way travel time to create a fish-depth static value; and
3) The fish depth static was applied to the data to correct for the vertical up and down movement of the Chirp fish and a final processed SEG-Y was output.
How accurate are the geographic locations?
Position data were provided by a Differential Global Positioning System (DGPS) navigation receiver. The Edgetech 512 Chirp fish was deployed 7m behind the DGPS receiver. Layback is estimated to be 7 ± 3m. No layback correction from the DGPS receiver position was applied to navigation data.
How accurate are the heights or depths?
Depths shown in the seismic data files are in milliseconds (round trip travel time) and are referenced to sea level. Vertical resolution is approximately 0.5 milliseconds and vertical accuracy is approximately ±4 milliseconds depending on sea state.
How consistent are the relationships among the observations, including topology?
Subbottom data were collected during USGS cruise S-5-09-SC using an Edgetech 512 Chirp subbottom profiling system consisting 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. Quality control was conducted during the collection process.
None. USGS-authored or -produced data and information are in the public domain.
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.
Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.
This information is not intended for navigational purposes.
U.S. Geological Survey, Pacific Coastal and Marine Science Center
2885 Mission Street
Santa Cruz, CA
What's the catalog number I need to order this data set?namss.S-5-09-SC.scs.chirp.zip – this zip file contains raw and processed high-resolution seismic-reflection (SEG-Y) and navigation (ASCII) data collected during PCMSC field activity S-5-09-SC. The data are divided up and presented by navigation line, as reflected in the individual file name(s).
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.