Archive of Digital Boomer Seismic Reflection Data Collected During USGS Cruise 97CCT01 Offshore of Central South Carolina, June 1997

The USGS Florida Integrated Science Center (FISC) - St. Petersburg assigns a unique identifier to each cruise or field activity. For example, 97CCT01 tells us the data were collected in 1997 for the Coastal Change and Transport (CCT) Project and the data were collected during the first field activity for that project in that calendar year. Refer to http://walrus.wr.usgs.gov/infobank/programs/html/definition/activity.html for a detailed description of the method used to assign the cruise ID. To differentiate between lines collected on different days, the date was added to the beginning of each trackline name. For example, line SB_1 collected on June 1 became line 601_SB_1, and line SB_1 collected on June 2 became line 602_SB_1. The boomer plate is an acoustic energy source that consists of capacitors charged to a high voltage and discharged through a transducer in the water. The transducer is towed on a sled at the sea surface and when discharged emits a short acoustic pulse, or shot, that propagates through the water and sediment column. The acoustic energy is reflected at density boundaries (such as the seafloor or sediment layers beneath the seafloor), detected by the receiver, and recorded by a PC-based seismic acquisition system. This process is repeated at timed intervals (e.g., 0.5 s) and recorded for specific intervals of time (e.g., 100 ms). In this way, a two-dimensional vertical image of the shallow geologic structure beneath the ship track is produced. A Huntec power supply provided 120-480 joules per shot. Reflected energy was received by an Innovative Transducers, Inc. (ITI) ST-5 streamer and recorded by Delph Seismic acquisition software. The streamer, which contains 10 hydrophones evenly spaced over a length of 6 m, was positioned parallel to the boomer sled and laterally separated from it by about 7 m. Refer to figure 1 included with this archive (Data Series 203) for a diagram of acquisition geometry. The sample frequency of the data was 16 kHz, and record length was 100-250 ms. Based on survey speeds of 3.5-4 knots and a shot rate of every 0.25-0.5 s, shot spacing was about 0.5-1 m. The unprocessed seismic data are stored in SEG-Y, integer, Motorola format, which is a standard digital format that can be read and manipulated by most seismic processing software packages (Barry and others, 1975). The SEG-Y formatted trace files have a .TRA extension. Additional recording parameters for each trace file can also be found in the .PAR file associated with each .TRA file. However, the .PAR and .PLN files included here are only needed to process or display the data with Delph Seismic software. Also provided are example Seismic Unix scripts that allow the user to strip off navigation fixes from the SEG-Y headers, along with a fix for every 500 shots, and produce a filtered and gained GIF image of each profile.