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2D Multichannel Seismic
Data Acquisition System
Bolt Airgun and Sentry Solid Streamer
U.S. Geological Survey
Started on June 5, 2011, and ended on June 25, 2011.
Number of Tracklines
In 2011, the U.S. Geological Survey (USGS) conducted a 2D MCS survey in support of U.S. extended continental shelf (ECS) assessments in the Gulf of Alaska. The survey was conducted with the R/V Marcus G. Langseth, a geophysical research vessel owned by the National Science Foundation and operated by Lamont-Doherty Earth Observatory of Columbia University.
This field survey were designed to determine sediment thickness and acoustic velocity in support of extended continental shelf maritime zone definition, conducted on behalf of the interagency U.S. Extended Continental Shelf Project, and are being released without restriction or warranty.
The final 4 MCS lines on L-09-11-GA, collected after June 21 (day 172/04:46 UTM), were collected using the offsets to the near 6 km of the streamer with 468 channels total due to a streamer malfunction.
Other Survey Identifiers
MGL1109 was used by Lamont-Doherty Earth Observatory.
Gulf of Alaska
Processed Data Classes
Data File Formats
Seismic Data Provenances
Digitally Acquired Digital SEG
The quality of the MCS data was excellent on the cruise. The only significant problem was encountered on L-09-11-GA (Gulf of Alaska) during data acquisition when a telemetry failure of the far 2 km of streamer occurred near the end of the survey (June 21). The airguns were powered down 18 times during L-09-11-GA, but these power-downs introduced significant data gaps only in line L0911-02. Most power-downs lasted 30 minutes or less. In these cases, with an 8 km streamer, the fold was reduced but no gap in the profile section resulted. During the survey, some variability in gun array volume and streamer depth occurred due to weather and maintenance requirements. This is documented in the observer logs for each acquisition line.
Field data were recorded in demultiplexed SEG-D format. Upon completion of an MCS profile line, SEG-D data files (one per shot) were posted to the ship’s server. These were concatenated into a single SEG-D file and imported to Paradigm’s Focus software for processing. Products of shipboard processing included raw shot gathers, CDP gathers processed through gapped predictive deconvolution, preliminary unmigrated stacked sections, post-stack FK-migrated sections, and stacking velocity fields. All MCS processing was reviewed and finalized post-cruise.
World Geodetic System 1984 (WGS84)
Tracklines 20 total
|Name||Length (km)||First SP||Last SP||First CDP||Last CDP|
|Field Activity Identifiers||L-09-11-GA, MGL1109|
|Vessels||R/V Marcus G. Langseth|
|Navigation System||C-Nav 3050|
|Horizontal Datum||World Geodetic System 1984|
|Recording System||Sercel Syntrak 960|
|Antenna to source||223 meters|
|Source to near channel||176 meters|
|Near channel number||636|
|Number of channels recorded||636|
|Number of cables||1|
|Number of channels each cable||636|
|Source to far channel||13 meters|
|Cable length||8,000 meters|
|Cable receiver depth||9 meters|
|Cable receiver depth recorded||Yes|
|Number of sources||36|
|Source array separation||8 meters|
|Source Depth||9 meters|
|Source volume||6,600 cubic inches|
|Source pressure||138 bars|
|Shot interval||50 meters|
|Sample interval||2,000 microseconds|
|Record length||15 seconds|