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| Titel |
Effect of the Free Core Resonance derived from tidal strain data |
| VerfasserIn |
Antonella Amoruso, Luca Crescentini, Vadim Milyukov, Aleksey Mironov, Andrey Myasnikov |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250140014
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| Publikation (Nr.) |
 EGU/EGU2017-3344.pdf |
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| Zusammenfassung |
| To investigate the effect of the Free Core Resonance (FCR) we use the data from two
European strain stations: Baksan (Russia), and Gran Sasso (Italy). Eight years of strain
recorded by two crossed 90-m long laser interferometers (BA and BC) at Gran Sasso
underground observatory, and six years of strain recorded by the 75-m long laser
interferometer at Baksan underground observatory, have been analysed.
For the FCR parameter estimation we use 8 diurnal tidal constituents (namely Q1, O1, P1,
K1, Ψ1, Φ1, J1, OO1) and compare measurements and model predictions through a joint fit
on BAKSAN, BA, and BC tidal parameters minimizing the £1 misfit function. As
measurements we use the amplitudes of the sine and cosine terms of the observed tides,
obtained from the output amplitudes and phases of the VAV03 code [Venedikov et
al., 2003] applied on the pre-whitened strain series. Retrieved tidal parameters are
corrected for ocean loading and local effects. Measured tidal parameters for the
three interferometers in the diurnal band have been compared with predicted SNRE
tides. The out-of-phase Φ1wave discrepancies are outside the uncertainties for all
interferometers, and the Baksan out-of-phase J1wave discrepancy is outside the uncertainty
too.
The results of analysis show that at the 80% (50%) confidence level the period of the Free
Core Nutation (TFCN) is between 413.5 (421.2) and 436.8 (431.0) sidereal days.
The quality factor is badly constrained because of the large uncertainty on the Ψ1
phase. Probability density function of Q-factor shows a peak around 18000. The
joint analysis confirms the results obtained from the analysis of the Gran Sasso
strain tides only [Amoruso et al., 2012] and are comparable to those from gravity
tides.
This work is partly supported by the Russian Foundation for Basic Research under Grant
No 16-05-00122.
References
Amoruso, A., Botta, V., Crescentini, L., 2012. Free Core Resonance parameters from
strain data:
sensitivity analysis and results from the Gran Sasso (Italy) extensometers. Geophys. J. Int.
189,
923-936.
Venedikov, A. P., Arnoso, J., Vieira, R., 2003. VAV: a program for tidal data processing.
Computers and Geosciences 29, 487-502.
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