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Petr Kolinsky Jiri Malek Institute of Rock Structure and Mechanics

Upper mantle of the Bohemian Massif (Central Europe) studied by surface waves from Kurile Islands M8.1 and M8.3 earthquakes. Petr Kolinsky Jiri Malek Institute of Rock Structure and Mechanics Academy of Sciences of the Czech Republic. AGU 2007 Fall Meeting December 1 0 – 14

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Petr Kolinsky Jiri Malek Institute of Rock Structure and Mechanics

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  1. Upper mantle of the Bohemian Massif (Central Europe) studied by surface waves fromKurile Islands M8.1 and M8.3 earthquakes Petr Kolinsky Jiri Malek Institute of Rock Structure and Mechanics Academy of Sciences of the Czech Republic AGU 2007 Fall Meeting December 10 – 14 San Francisco, CA, USA

  2. contents motivation data surface wave analysis polarization phase velocity dispersion curves structure conclusion contents motivation data surface wave analysis polarization phase velocity dispersion curves structure conclusion Kolinsky and Malek: Upper mantle of the Bohemian Massif

  3. motivation - structural: Bohemian Massif - former project on crustal velocity estimation 9 – 36 s, 40 km depth - can we look at the deeper structure of the same region? contents motivation data surface wave analysis polarization phase velocity dispersion curves structure conclusion Kolinsky and Malek: Upper mantle of the Bohemian Massif

  4. motivation - methodological surface wave studies are included in the PASSEQ project surface wave phase velocity analysis "long" period phase velocity measured at "short" distances "long" period: up to 200 s "short" distances: around 150 km contents motivation data surface wave analysis polarization phase velocity dispersion curves structure conclusion Kolinsky and Malek: Upper mantle of the Bohemian Massif

  5. contents motivation data surface wave analysis polarization phase velocity dispersion curves structure conclusion Kurile Islands M 8.1 and M 8.3 8.600 km Scotia Sea M 7.0 13.000 km Kolinsky and Malek: Upper mantle of the Bohemian Massif

  6. contents motivation data surface wave analysis polarization phase velocity dispersion curves structure conclusion Kolinsky and Malek: Upper mantle of the Bohemian Massif

  7. contents motivation data surface wave analysis polarization phase velocity dispersion curves structure conclusion • Guralp • 150 km • Guralp STS-2 170 km STS-2 Kolinsky and Malek: Upper mantle of the Bohemian Massif

  8. STS-2 (natural period 120 s) 60 s 150 s Guralp (natural period 30 s) 60 s 150 s contents motivation data surface wave analysis polarization phase velocity dispersion curves structure conclusion Kolinsky and Malek: Upper mantle of the Bohemian Massif

  9. surface wave analysis contents motivation data surface wave analysis polarization phase velocity dispersion curves structure conclusion • multiple filtering • Gaussian filters • constant relative resolutionfiltering • instantaneous period estimation Kolinsky and Malek: Upper mantle of the Bohemian Massif

  10. contents motivation data surface wave analysis polarization phase velocity dispersion curves structure conclusion frequency-time spectrogram and truncated fundamental mode spectrogram velocity (km/s) velocity (km/s) period (s) period (s) Kolinsky and Malek: Upper mantle of the Bohemian Massif

  11. contents motivation data surface wave analysis polarization phase velocity dispersion curves structure conclusion set of harmonic signals Kolinsky and Malek: Upper mantle of the Bohemian Massif

  12. particle motion in horizontal plane contents motivation data surface wave analysis polarization phase velocity dispersion curves structure conclusion Kuril Islands continental path 8700 km Scotia Sea oceanic path 13000 km Kolinsky and Malek: Upper mantle of the Bohemian Massif

  13. contents motivation data surface wave analysis polarization phase velocity dispersion curves structure conclusion set of coherent harmonic signals at two stations (time shift = 41 s) Kolinsky and Malek: Upper mantle of the Bohemian Massif

  14. T = 50 s T = 100 s T = 150 s    contents motivation data surface wave analysis polarization phase velocity dispersion curves structure conclusion 43.51 s 41.71 s 39.95 s Kolinsky and Malek: Upper mantle of the Bohemian Massif

  15. Love continental group velocity contents motivation data surface wave analysis polarization phase velocity dispersion curves structure conclusion Rayleigh continental Love oceanic Rayleigh oceanic Love PREM Rayleigh PREM Kolinsky and Malek: Upper mantle of the Bohemian Massif

  16. phase velocity contents motivation data surface wave analysis polarization phase velocity dispersion curves structure conclusion Kolinsky and Malek: Upper mantle of the Bohemian Massif

  17. structure – inversion problem contents motivation data surface wave analysis polarization phase velocity dispersion curves structure conclusion - the dispersion curves are computed by matrix method Proskuryakova et al. (1981) - it uses modified Thomson – Haskell matrices - Isometric Method (IM) was developed for solving weakly non-linear inverse problems with many parameters Malek et al. (2005 and 2007) Kolinsky and Malek: Upper mantle of the Bohemian Massif

  18. contents motivation data surface wave analysis polarization phase velocity dispersion curves structure conclusion inversion non-uniqueness - similar dispersion curves may correspond to different velocity models - measured dispersion points can be fitted by different smooth dispersion curves Kolinsky and Malek: Upper mantle of the Bohemian Massif

  19. contents motivation data surface wave analysis polarization phase velocity dispersion curves structure conclusion parameters - during Love wave phase velocity inversion we look for vS model - during Rayleigh wave phase velocity inversion we look for vS and vP/vS ratio - depths of interfaces are fixed during the inversion Kolinsky and Malek: Upper mantle of the Bohemian Massif

  20. inversions contents motivation data surface wave analysis polarization phase velocity dispersion curves structure conclusion Kolinsky and Malek: Upper mantle of the Bohemian Massif

  21. contents motivation data surface wave analysis polarization phase velocity dispersion curves structure conclusion velocity distribution Z - component R - component T - component Kolinsky and Malek: Upper mantle of the Bohemian Massif

  22. contents motivation data surface wave analysis polarization phase velocity dispersion curves structure conclusion Kolinsky and Malek: Upper mantle of the Bohemian Massif

  23. conclusions contents motivation data surface wave analysis polarization phase velocity dispersion curves structure conclusion - phase velocities in the period range of 30 – 200 s were studied at the short station distances of 150 and 170 km - Rayleigh wave phase velocity dispersion curves are well pronounced in the whole period range - Love wave phase velocity dispersion curves are well pronounced only in limited period range of 30 – 110 s - continental path gives clearer Rayleigh wave fundamental mode while oceanic path gives clearer Love wave fundamental mode - Rayleigh waves from Z and R components give slightly different results (anisotropy?) - S-wave velocity in the upper mantle of the Bohemian Massif reaches minimum around the depth of 130 km Kolinsky and Malek: Upper mantle of the Bohemian Massif

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