Calibrating broad-band seismometers in the extreme cold : Application to the observatory station CCD (Concordia, DomeC, Antarctica)
Abstract
The first year-round continuous broad-band recordings at the Concordia observatory station in East Antarctica (CCD) started in 2005. For the first two years, technical problems due to the extreme cold conditions (the seismic vault is at a constant temperature of -54°C) resulted in data whose quality was too poor to permit distribution. Since January 2007, the data from CCD have been officially open to any researchers who wish to request them directly to the operators. Such requests have been honored to the best of our ability, taking into account the delay for the data being shipped from Concordia to Europe (we receive data once a year, at the end of the summer field season in Antarctica). Up to now, we have only been able to provide nominal seismometer responses along with the data, despite suspecting that the extreme cold could affect the characteristics of the instruments. After several unsuccessful attempts in early 2008, 2009 and 2010, we finally succeeded in calibrating the seismometers in situ in early 2011. Here we present the design of our cold-tested calibration box, and the results of the direct calibrations of two instruments that were running in 2011 : an STS-2 running at -30°C (i.e. above the ambient temperature in the vault), and a T240 running at -54°C. We have found the response of the "warm" STS-2 to be near nominal, while that of the "cold T240" differs substantially from its nominal response. Furthermore, during the time period 2007-2009, the "warm" STS-2 was running alongside an identical but unheated STS-2, for which we shall present a relative calibration. Thanks to these calibrations, we shall shortly be able to distribute the Concordia data more widely, via the data centers at Geoscope and IRIS.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2011
- Bibcode:
- 2011AGUFM.S51A2184B
- Keywords:
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- 7294 SEISMOLOGY / Seismic instruments and networks