Abstract:
In 2015 long offset seismic gathers were collected at Korff Ice Rise, West Antarctica, with the aim of studying fabric within the ice column and ice bed properties. Data were collected at sites within 700m of one another along the axis of the ice divide. The seismic gathers were collected at 60 deg intervals to study azimuthal variation in seismic velocity and shear wave splitting.
This study is part of the British Antarctic Survey programme Polar Science for Planet Earth. All data were collected with the support of the British Antarctic Survey.
Keywords:
Anisotropy, Fabric, Polarimetry, Seismic
Brisbourne, A., & Smith, A. (2018). Multi-azimuth long-offset seismic gathers from Korff Ice Rise, West Antarctica, 2015 (Version 1.0) [Data set]. Polar Data Centre, Natural Environment Research Council, UK Research & Innovation. https://doi.org/10.5285/c563569e-0875-404b-acb2-cd5f9e5c4706
| Access Constraints: | No restrictions apply. |
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| Use Constraints: | This data is governed by the NERC data policy http://www.nerc.ac.uk/research/sites/data/policy/ and supplied under Open Government Licence v.3 http://www.nationalarchives.gov.uk/doc/open-government-licence/version/3/ |
| Creation Date: | 2018-09-20 |
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| Dataset Progress: | Complete |
| Dataset Language: | English |
| ISO Topic Categories: |
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| Parameters: |
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| Personnel: | |
| Name | UK PDC |
| Role(s) | Metadata Author |
| Organisation | British Antarctic Survey |
| Name | Alexander M Brisbourne |
| Role(s) | Technical Contact, Investigator |
| Organisation | British Antarctic Survey |
| Name | Andrew M Smith |
| Role(s) | Technical Contact, Investigator |
| Organisation | British Antarctic Survey |
| Parent Dataset: | N/A |
| Reference: | Submitted to JGR Earth Surface: Constraining Recent Ice Flow History at Korff Ice Rise, West Antarctica, Using Radar and Seismic Measurements of Ice Fabric, A. M. Brisbourne, C. Martín, A. M. Smith, A. F. Baird, J. M. Kendall, and J. Kingslake Nicholls, K. W., Corr, H. F. J., Stewart, C. L., Lok, L. B., Brennan, P. V., & Vaughan, D. G. (2015). A ground-based radar for measuring vertical strain rates and time-varying basal melt rates in ice sheets and shelves. Journal of Glaciology, 61(230), 1079-1087. doi:10.3189/2015JoG15J073 |
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| Quality: | 8000Hz sample rate with GPS shot trigger timing; 24 bit recording | |
| Lineage: | The three gathers were oriented at 60° to one another to constrain azimuthal variation in seismic properties centred on a single site on the axis of the divide. Each gather used four shot points, each with 48 receivers at 10m intervals. The offset to the first receiver ranged from 30 to 1440m, producing traces out to 1940m offset, or incidence angle at the bed up to 58°. To achieve three-component recordings, the receivers were oriented to measure either vertical, radial or transverse motion. The CMP gather along the divide axis (K01; true bearing 043°) was shot twice: once with all sensors orientated vertically using 150g of high explosive, and once with horizontal sensors alternating radial and transverse orientation, using 600g shots; the latter resulting in an effective 20m receiver interval for the horizontal components. The oblique CMP gathers (K02: 60° east of K01; K03: 60° west of K01) were shot once only, each with 600g shots and alternating vertical, radial and transverse receivers, resulting in an effective 30m receiver interval for all three components. The larger shot is required to generate sufficient S-wave energy at the source. Although an explosive source in a homogeneous isotropic medium will theoretically not generate S-wave energy, the non-uniform nature of the shallow firn results in significant S-wave energy. The acquisition geometry results in a mid-point basal reflection ellipse with a length of 235m. | |
| Temporal Coverage: | |
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| Start Date | 2015-01-01 |
| End Date | 2015-01-31 |
| Spatial Coverage: | |
| Latitude | |
| Southernmost | -78.714 |
| Northernmost | -78.714 |
| Longitude | |
| Westernmost | -68.414 |
| Easternmost | -68.414 |
| Altitude | |
| Min Altitude | N/A |
| Max Altitude | N/A |
| Depth | |
| Min Depth | N/A |
| Max Depth | N/A |
| Location: | |
| Location | Antarctica |
| Detailed Location | Korff Ice Rise |
| Data Collection: | Instrumentation: Recorded on 2 x 24 channel Geometrics Geode with 48 x 40Hz Georods; Source: 150-600g high explosive shots at 20 m depth. Resolution: The Fresnel zone is less than 80 m (minimum 150 Hz dominant frequency). 1940m maximum offset. |
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| Data Storage: | 4 files of IBM Real SEGY written by Promax v5000.10; 2 sec records, 192 channels, 30 m offset, 10m channel interval, geometry is assigned but no processing has been included. K01_AVO_Z.segy - Line KO1 vertical sensors only K01_AVO_R_T.segy - Line KO1 alternating radial and transverse sensors K02_AVO_Z_R_T.segy - Line KO2 alternating vertical, radial and transverse sensors K03_AVO_Z_R_T.segy - Line KO3 alternating vertical, radial and transverse sensors |
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