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Seismological calibration of arrays

O'Mongain, Aoife M.. 2004 Seismological calibration of arrays. Nottingham, UK, British Geological Survey, 29pp. (IR/04/056) (Unpublished)

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Abstract/Summary

The UK is responsible for the seismological calibration of the array station EKA which contributes data to the International Monitoring System (IMS) of the Comprehensive Test Ban Treaty Organisation (CTBTO). Such calibration includes the provision of seismic travel time corrections for the array station to allow for local velocity variations on the propagation path from seismic events at different distances and azimuths. The EC ARI Framework funded a two-part investigation into techniques for facilitating seismological calibration of seismic arrays. In the first part, analysis of variance was applied to manually picked arrival times at EKA from local events. Four bins of event data at different distances and azimuths were examined and for most the station correction time terms were found to be smaller than the sample rate of the instruments (0.05 seconds). Travel time residuals from each source-station pair were also examined and some distance and azimuth dependency was found. Slowness and azimuth values were recalculated once the station correction terms were applied to the data. Large discrepancies were found between the observed slowness values and those of the standard earth model IASPEI91, indicating significant differences between the local velocity structure and the IASPEI model. The second part of the work examined automatic arrival time pickers in order to expedite the calibration procedure and extend the study to more bins of data. Analysis of variance was used to investigate the picking accuracy and two methods (a cross correlation method and an Auto-Regressive Akaike Information Criterion method (ARAIC)) were tested. The results showed that in most cases the cross correlation method proves to be even more accurate than manual picking (having a variance of less than 0.001s2 in most cases) while the ARAIC method is not as successful on this data set.

Item Type: Publication - Report (UNSPECIFIED)
Programmes: BGS Programmes > Seismology and Geomagnetism
Funders/Sponsors: British Geological Survey
Additional Information. Not used in RCUK Gateway to Research.: This item has been internally reviewed but not externally peer-reviewed
Date made live: 09 Jan 2015 09:14 +0 (UTC)
URI: http://nora.nerc.ac.uk/id/eprint/509288

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