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UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS Guest
2024-11-22 2:08 |
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Conference: Bucharest University Faculty of Physics 2007 Meeting
Section: Atmosphere and Earth Science; Environment Protection
Title:
Slowness corrections – One way to improve single-array location capabilities
Authors:
Daniela Ghica(1), Johannes Schweitzer(2)
Affiliation:
1) National Institute for Earth Physics, 12 Calugareni St., 077125, PO Box MG-2 Magurele, Romania
2) NORSAR, Instituttveien 25, 2007 Kjeller, Norway
E-mail
daniela@infp.ro, daniela_ghica@yahoo.com
Keywords:
array seismology, slowness corrections, array calibration
Abstract:
Seismic arrays are powerful tools, mainly for improving the signal-to-noise ratio and detecting distant events otherwise masked by the background noise. It was already demonstrated that seismic arrays using the specific analysis techniques, are superior to single three-component stations, for detecting and characterizing signals and explosions.
The first step to identify and locate a seismic event with an array is the association of observed onsets with well-known seismic sources. Well-defined slowness measurements are very useful for associating seismic phases to presumed seismic events.
Shortly after installation of the first seismic array in Romania, Bucovina Romanian Seismic Array (BURAR), systematic discrepancies between measured and theoretically predicted slowness values were observed, especially for the regional phases. Consequently, slowness measurements of BURAR seismic station should be calibrated. A calibration technique for the seismic monitoring with BURAR system was introduced, by applying the correction of measured slowness with seismic phases observed by the station.
Data sources of the study consisted of BURAR recordings during time interval: 1 January 2005 – 31 December 2006. For events identification, PDE monthly and weekly bulletins (59962 worldwide events) and Romanian Earthquake Catalogue (1785 local & regional events) were used.
Mean slowness corrections could be defined and estimated with their standard deviations, by investigation of all automatically detected and analyzed phases (apparent velocity or ray parameter and azimuth parameters), to search for systematic patterns in slowness deviations. 400 slowness-corrections vectors were calculated; mean slowness deviation is 2.039 s/deg. Slowness-corrections vectors obtained were applied for re-locating local and regional seismic events in order to calibrate BURAR station.
After associating slowness-corrections with seismic phases observed by BURAR, the single array location capabilities were significantly improved. Information obtained will be also essential in further studies on sources, structure and wave propagation, both on local and regional scale.
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