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Data Set ID:
NSIDC-0349

Iceberg Harmonic Tremor, Seismometer Data, Antarctica, Version 1

Seismometers were placed on a 25 km by 50 km iceberg called C16 in the Ross Sea, Antarctica, to identify the Iceberg harmonic Tremor (IHT) source mechanism and to understand the relevance of IHT to iceberg calving, drift and break-up. The seismic observations reveal that the IHT signal consists of extended episodes of stick-slip icequakes (typically thousands per hour) generated when the ice-cliff edges of two tabular icebergs rub together during glancing, strike/slip type iceberg collisions (e.g., between C16 and B15A). With the source mechanism revealed, IHT may provide a promising signal useful for the study of iceberg behavior and iceberg-related processes such as climate-induced ice-shelf disintegration.

Here, a single day of seismometer data for a single station on iceberg C16 is provided as an example of "a day in the life of an iceberg" for use by scientists and students wishing to know more about IHT. The station data is from C16 "B" site on C16's northeast corner, and the day is 27 December, 2003, a day when B15A struck C16 and caused an episode of tremor that was particularly easy to identify and understand.

This represents only a small fraction of the total data that exist for the seismic program on iceberg C16. The full data are archived at the IRIS data center (where seismic data is commonly archived). This one-day data set is to provide glaciologists with ready access to a good example of IHT that they can use for teaching and for demonstration purposes. Data are available in comma-delimited ASCII format and Matlab native mat files. Data are available via FTP.

Geographic Coverage

Spatial Coverage:
  • N: -77, S: -77, E: 168, W: 168

Spatial Resolution: Not Specified
Temporal Coverage:
  • 27 December 2003 to 28 December 2003
Temporal Resolution: Not specified
Parameter(s):
  • Glaciers/Ice Sheets
  • Sea Ice > Icebergs
  • Glaciers/Ice Sheets > Icebergs
  • Snow/Ice > Ice Motion
  • Sea Ice > Sea Ice Motion
Platform(s) FIELD INVESTIGATION, FIELD SURVEYS
Sensor(s): Not specified
Data Format(s):
  • ASCII Text
Version: V1
Data Contributor(s): Douglas MacAyeal, Emile Okal, Richard Aster, Jeremy Bassis

Data Citation

As a condition of using these data, you must cite the use of this data set using the following citation. For more information, see our Use and Copyright Web page.

MacAyeal, D. R., E. Okal, R. Aster, and J. Bassis. 2008. Iceberg Harmonic Tremor, Seismometer Data, Antarctica, Version 1. [Indicate subset used]. Boulder, Colorado USA. NSIDC: National Snow and Ice Data Center. doi: http://dx.doi.org/10.7265/N5445JD6. [Date Accessed].

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Detailed Data Description

Format

Space delimited ASCII, one header line. The data for each channel are stored as Albuquerque Seismic Lab (ASL) format in an ascii text file. To read the data, the header gives the station name, channel, start time and sample rate. Following the header (one line only) is the time series.

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File Naming Convention

File is named according to the following convention:

.HHN: 100 hertz sample rate (HH), North (N)


HHZ, HHE and HHN are standard seismological variables, they stand for the 100Hz vertical, east and north seismometer channel readings (HH says "100 hz sample rate" and Z, E or N appended on tells the channel, or component of motion.)

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Volume

Approximately 150 Megabytes

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Spatial Coverage

Southernmost Latitude: 78 South 
Northernmost Latitude: 78 South 
Westernmost Longitude: 178 West 
Easternmost Longitude: 178 West

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Temporal Coverage

27 December 2003 to 28 December 2003, 100 Hz sample rate

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Parameter or Variable

Parameters include: seismology, harmonic tremor, iceberg, Antarctica, Ross Ice Shelf

Sample Data Record


To read the data, the header gives the station name, channel, start time and sample rate. 
Following the header (one line only) is the time series.

The header is: C16B HHN 03 361 00 00 24 78 100.00 8625661 1.265E8 50 GSNVBB1

C16B 
HHN
03
361
00
00
24
78
100.00
8625661
1.265E8
50
GSNVBB1
-3824
-3635
-3419
-3357
-3276
-2820
-2962
-3278
-3139
-3511
-2867
-2250
-2546
-2109
-1675
-1475
-1473
-1644
-1721
-1288
-549
-1664
-2427
-1904
-1989
-1542
-1688
-2573
-2981
-2766
-2390
-2344
-2636
-2967
-3054
-3403
-3044
-3337
-3841
-3787
-4369
-4047
-3824
-3554
-3182
-3576
-3598
-3571
-3988
-4460
-4433
-4359
-4330
-4396
-4703
-4560
-4374
-4674
-4773
-4774
-4801
-4530
-4624
-4768
-5056
-5371
-5156
-5146
-4910
-4564
-4624
-4673
-4900
-4953
-4774
-4755
-4705
-4670
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Software and Tools

An example of Matlab code used to read the data is provided below.

Please visit The Incorporated Research Institutions for Seismology (IRIS) for more information.

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Data Acquisition and Processing

Data Acquisition Methods

Data were collected on 3 channels (east, north and vertical) at a sample rate of 100 Hz. The seismometer was placed in a shallow snow pit on iceberg C16 near its northeast corner. Operation was powered by a solar-charged 12-volt battery.

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Sensor or Instrument Description

A three-component Guralp 40T seismometer digitized by a Quanterra Q330

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References and Related Publications

Contacts and Acknowledgments

Douglas MacAyeal
Department of Geophysical Sciences
University of Chicago
5734 S. Ellis Ave. 
HGS 413
Chicago, Illinois 60637 USA

Emile Okal 
Department of Earth and Planetary Sciences 
Northwestern University 
Evanston, Illinois 60208-2150, USA

Richard Aster
Dept of Earth & Environmental Science
New Mexico Tech 
Socorro, New Mexico 87801 USA

Jeremy Bassis
Institute for Geophysics and Planetary Physics
Scripps Institution of Oceanography
University of California, San Diego
La Jolla, California, 92093-0225 USA

Acknowledgements: 

This research was supported by National Science Foundation (NSF) Office of Polar Programs (OPP) grant 0229546 awarded to D. MacAyeal.

Document Information

DOCUMENT CREATION DATE

October 2008

No technical references available for this data set.
No FAQs or How Tos available for this data set.

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