HR: 1340h
AN: S33A-0295    [Abstracts]
TI: How to highlight the Earth's free oscillations from discontinuous datasets? Application to the 26 December 2004 Sumatra-Andaman Earthquake.
AU: Houlie, N
EM: houlie@ipgp.jussieu.fr
AF: Institut de Physique du Globe de Paris Equipe de Sismologie case 89, 4, Place Jussieu, Paris 05, 75252 France
AU: * Roult, G
EM: groult@ipgp.jussieu.fr
AF: Institut de Physique du Globe de Paris Equipe de Sismologie case 89, 4, Place Jussieu, Paris 05, 75252 France
AU: Clévédé, E
EM: clevede@ipgp.jussieu.fr
AF: Institut de Physique du Globe de Paris Equipe de Sismologie case 89, 4, Place Jussieu, Paris 05, 75252 France
AU: Mignard, F
EM: francois.mignard@obs-nice.fr
AF: Observatoire Cote d'Azur / Cassiopee, Le Mont Gros BP4229, Nice 04, 06304 France
AB: The high quality of the GEOSCOPE and FDSN seismological broad-band stations contributes to the clear observation of seismic normal modes at frequencies lower than 2mHz and offers a good opportunity for studying the behaviour of these modes. The interest of scientists for the gravest normal modes is due to the fact that they do contribute to a better knowledge of the density profile in the Earth, helping to constrain Earth's models. These modes have been clearly identified after some large recent events. The Mw = 9.3 Sumatran earthquake of December 2004 provides us with individual spectra which exhibit a clear splitting of the gravest spheroidal modes (0S2 - 0S5.) and a precise identification of each of the individual singlets, with a resolution on frequencies and Q quality factors never obtained in the past. The accuracy of the eigenfrequencies of the gravest spheroidal modes including the radial mode 0S0 is discussed. The difficulty for getting very long time series without any problems (glitches, gaps, trends, jumps.. ) is well known. Thus, very often, the available recordings are too short to complete successfully the frequency analysis, even for the Sumatran event (Park et al., Science 2005). We present results obtained from a frequency analysis from recordings with discontinuities. On selected 10-days (or 20-days) discontinuous recordings we applied the FAMOUS method (Mignard, 2005). Comparisons between the eigenfrequencies computed using classical Fast Fourier Transform (FFT) and FAMOUS algorithms are presented.
DE: 7255 Surface waves and free oscillations
DE: 7294 Seismic instruments and networks (0935, 3025)
SC: Seismology [S]
MN: Fall Meeting 2005