Boomer Seismic Reflection Profiles and Shotpoint Navigation Collected on USGS Field Activities 01ASR01, 01ASR02, 02ASR01, and 02ASR02,Miami, Florida, November and December, 2001, and January and February, 2002.

Seismic reflection profiles are acquired by means of an acoustic source (usually generated electronically) and a hydrophone or hydrophone array. Both elements are typically towed in the water behind a survey vessel. The sound source emits a short acoustic pulse, which propagates through the water and sediment columns. The acoustic energy is reflected at density boundaries (such as the seafloor or sediment layers beneath the seafloor) and detected at the hydrophone. This process is repeated at intervals ranging between 100 ms and 1s depending on the source type. In this way, a two-dimensional image of the geologic structure beneath the ship track is constructed. Seismic data were stored in SEG-Y format, which is a standard digital format that can be read and manipulated by most seismic-processing software packages. The data presented in this appendix are the processed profiles only. These data are stored in GIF-formatted image files. For Field Activity 01ASR01, the seismic source employed consisted of a boomer transducer towed on a sled at the sea surface providing 100 joules per shot. The reflected energy was received by an SN Technologies NexGen solid core streamer and recorded by PC-based Triton-Elics Delph Seismic acquisition software. The streamer contains 10 hydrophones evenly spaced every 2 meters. Only data received by elements 7 and 8 were summed for line 01b01 and for line 01b02 through shot number 2,819. Afterward, only data received by elements 8 and 9 were summed. The streamer was positioned parallel to the boomer sled and laterally separated from it by approximately 3 m. The sled was towed approximately 5 m behind the GPS antenna. The sample frequency of the data was 12 KHz and the total record length was 100 ms. The fire rate was every 0.5 s, which resulted in a shot spacing of about 0.64 m. For Field Activity 01ASR02, the seismic source employed consisted of a boomer transducer towed on a sled at the sea surface providing 280 joules per shot. The reflected energy was received by an SN Technologies NexGen solid core streamer and recorded by PC-based Triton-Elics Delph Seismic acquisition software. The streamer contains 10 hydrophones evenly spaced every 2 meters. Only data received by elements 8 and 9 where summed for line 01b01 through shot number 8,903. Afterward, data received by element 10 was also summed. The streamer was positioned parallel to the boomer sled and laterally separated from it by approximately 3 m. The sled was towed approximately 5 m behind the GPS antenna. The sample frequency of the data was 24 KHz and the total record length was 100 ms. The fire rate was every 0.5 s, which resulted in a shot spacing of about 0.64 m. For Field Activity 02ASR01, the seismic source employed consisted of a boomer transducer towed on a sled at the sea surface providing 280 joules per shot. The reflected energy was received by an SN Technologies NexGen solid core streamer and recorded by PC-based Triton-Elics Delph Seismic acquisition software. The streamer contains 10 hydrophones evenly spaced every 2 meters. Only data received by elements 8, 9, and 10 were summed for line 02b01 and for line 02b02 through shot number 1,748. Only data received by elements 5, 6, and 7 were summed for line 02b02 between shot numbers 1,750 and 2,828. For the rest of line 02b02 and for all other lines, only data received by elements 4, 5, and 6 were summed. The streamer was positioned parallel to the boomer sled and laterally separated from it by approximately 3 m. The sled was towed approximately 5 m behind the GPS antenna. The sample frequency of the data was 12 KHz for line 02b01 and 24 KHz for all other lines. The total record length was 100 ms. The fire rate was every 0.5 s, which resulted in a shot spacing that ranges from about 0.46 m to 0.64 m. For Field Activity 02ASR02, the seismic source employed consisted of a boomer transducer towed on a sled at the sea surface providing 280 joules per shot. The reflected energy was received by an Innovative Transducer, Inc. (ITI) solid core streamer and recorded by PC-based Triton-Elics Delph Seismic acquisition software. The streamer contains 10 hydrophones evenly spaced about every 0.6 m (2 ft). However, only data received by elements 3 and 4 were summed. The streamer was positioned parallel to the boomer sled and laterally separated from it by approximately 3.5 m. The sled was towed approximately 5.5 m behind the GPS antenna through shot number 8,230 of line 02b01, and approximately 7.5 m behind the antenna for the rest of the line. The sample frequency of the data was 24 KHz and the total record length was 100 ms. The fire rate was every 0.5 s, which resulted in a shot spacing that ranges from about 0.46 m to 0.64 m. Differential GPS navigation was fed to the acquisition system every second by a WAAS/Beacon DGPS receiver. The accuracy of this receiver is to within 5 m. However, the data required some editing. These edited results were used to generate the trackline maps presented here. However, the navigation data has not been corrected to reflect the offset between the source and the GPS antenna. Position fixes for every 500 shots and for the start of line are also provided as an aide for registering of the data after plotting. The trackline maps provided in this appendix are in geographic projection. They were created using ESRI's GIS software ArcView 3.2, exported to Adobe Illustrator for further editing, and saved as GIF images. These GIF images are viewable with your WWW browser. All navigation files are stored as flat ASCII text files.