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Addendum 1.0 to SCAR Report #9 (August 1992) Data-collector costs and data submission for CD-ROM production |
SCAR Report 9 |
| Addendum 1.0 | Appendix A | Appendix I | Appendix II | Appendix III |
| Appendix B | Appendix C | Appendix D | Appendix E | Appendix F |
Appendix C: Example of a cruise report (Minimum information is shown,
but more information is preferred.)
R.R.S. DISCOVERY CRUISE 154
INTRODUCTION
In January-March 1985 the British Antarctic Survey and University of Birmingham conducted marine geological and geophysical surveys off the Antarctic Peninsula, in the Weddell Sea, over the South Orkney Microcontinent, and over the southern South Sandwich Island Arc. This cruise collected approximately 3770 km of 24-fold multichannel seismic reflection (MCS) data. The surveys extended between 24 and 68 degrees west longitude, and between 59 and 68 degrees south latitude. The MCS data collected off the Antarctic Peninsula (lines AMG845-01 to AMG845-14) were included on SDLS CD-ROM no. 16.
The surveys were carried out on R.R.S. DISCOVERY. The digital MCS data were recorded on a SERCEL 358 system with input from a 96-channel TELEDYNE streamer via a DSS-V interface. The analog signals from pairs of streamer channels were summed before being input to the recording system so that the digitized data are effectively from 48 x 50 m-long hydrophone groups. The source consisted of an airgun array with a total volume of 8.5 liters fired approximately every 50 meters. A TRANSIT satellite receiver system was used for navigation.
Processing of the data generally followed a conventional sequence:
demultiplexing, spherical divergence correction, shot-by-shot designature, deconvolution, velocity analysis, normal moveout correction, pre-stack mute, offset weighted stack, 3-trace running mix, time- and space-variant bandpass filter, and display scaling.
These data are brute stack without any post-stack processing (with the exception of line AMG845-17).
DATA ORGANIZATION
There are 8 seismic reflection profiles from cruise 154 for a total of 1573.950 km.
| Line | First shot point |
Last shot point |
Length (Km) |
Region |
| AMG845-15 | 1 | 16795 | 839.700 | northwest Weddell Sea |
| AMG845-16 | 1 | 3360 | 167.950 | South Orkney Microcontinent |
| AMG845-17 | 1 | 2337 | 116.800 | South Orkney Microcontinent |
| AMG845-18 | 1 | 2146 | 107.250 | South Orkney Microcontinent |
| AMG845-19 | 1 | 1215 | 60.700 | South Sandwich Island Arc |
| AMG845-20 | 1 | 2371 | 118.50 | South Sandwich Island Arc |
| AMG845-21 | 1 | 832 | 41.550 | South Sandwich Island Arc |
| AMG845-24 | 1 | 400 | 19.950 | South Sandwich Island Arc |
| Total | 1573.950 |
The data are recorded in 17 SEG-Y format (32bit IEEE floating point) files, and files are separated by one one end-of-file mark. The data were originally processed by GECO (UK). With the exception of line AMG845-17 (see below), no post-stack processing has been applied to the data. The same processing sequence was used for all lines, with the following exceptions:
| 1. | The "designature" process (a wavelet shaping procedure to reduce variations in source signature between different shots) was not used on line AMG845-15. |
| 2. | No deconvolution before stack was carried out on line AMG845-15 |
| 3. | For line AMG845-16, -17, -18 the prediction lag used in deconvolution before stack was 24 ms, while for line AMG845-19, -20, -21, -24the prediction lag was 36 ms. The deconvolution operator length for all these line was 300ms. |
| 4. | Line AMG845-16 has been reprocessed by British Antarctic Survey. The processing sequence was basically the same as originally used by GECO (UK). However, instead of the GECO designature process a simple bandpass filter with corner frequences at 9Hz and 70 Hz was applied, and instead of the offset weighting function applied by GECO (X/X+L which means offset divided by the sum of offset plus maximum offset), a directly proportional to the receiver offset trace wighting was applied. Minor offsets in the sea-floor reflection at about CDP 2260 and 3040 are processing artefacts. |
| 5. | The original stack data for line AMG845-17 and the eastern part of line AMG845-20 are no longer retreivable. The data included on the CD-ROM for line AMG845-17 were obtained by scanning a paper print of the original stack. |
OWNERSHIP
Users who have questions regarding the multichannel seismic data or who wish to obtain permission (prior to 8 years following data collection) to use these data for cooperative research should contact:
Dr. Robert Larter
British Antarctic Survey
High Cross, Madingley Road
Cambridge, England CB3 0ET
Publications based on data included
Barker P.F., Kennett J.P & Shipboard Party, 1988a. Weddell Sea Palaeoceanography: preliminary results of Leg 113. Palaeogeography, Palaeoclimatology, Palaeoecology, 67, 75-102.
Barker P.F., Kennett J.P. & Shipboard Party, 1988b. Proc ODP, Init. Repts., 113. College Station, TX (Ocean Drilling Program).
Hamilton I.W., 1989. Geophysical investigations of subduction-related processes in the Scotia Sea. Ph.D. thesis, Univ. of Birmingham, Birmingham, England, 328 pp.
Lonsdale M.J., 1990. The relationship between silica diagenesis, methane and seismic reflections on the South Orkney microcontinent.Proc. ODP, Sci. Results, 113, 27-37.
Oszko, L., 1996. Tectonic structures and glaciomarine sedimentation in the southeastern Weddell Sea from seismic reflection data. Ph.D. thesis, Univ. of Bremen, Bremen, Germany. Berichte zur Polarforschung, 222.
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