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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.

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Presentation on theme: "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."— Presentation transcript:

1 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 10 – 14 San Francisco, CA, USA

2 Kolinsky and Malek: Upper mantle of the Bohemian Massif2 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

3 Kolinsky and Malek: Upper mantle of the Bohemian Massif3 contents motivation data surface wave analysis polarization phase velocity dispersion curves structure conclusion 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?

4 Kolinsky and Malek: Upper mantle of the Bohemian Massif4 contents motivation data surface wave analysis polarization phase velocity dispersion curves structure conclusion 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

5 Kolinsky and Malek: Upper mantle of the Bohemian Massif5 contents motivation data surface wave analysis polarization phase velocity dispersion curves structure conclusion Kurile Islands M 8.1 and M km Scotia Sea M km

6 Kolinsky and Malek: Upper mantle of the Bohemian Massif6 contents motivation data surface wave analysis polarization phase velocity dispersion curves structure conclusion

7 Kolinsky and Malek: Upper mantle of the Bohemian Massif7 contents motivation data surface wave analysis polarization phase velocity dispersion curves structure conclusion STS km STS-2 Guralp 150 km Guralp

8 Kolinsky and Malek: Upper mantle of the Bohemian Massif8 contents motivation data surface wave analysis polarization phase velocity dispersion curves structure conclusion STS-2(natural period 120 s) 60 s 150 s Guralp(natural period 30 s) 60 s 150 s

9 Kolinsky and Malek: Upper mantle of the Bohemian Massif9 contents motivation data surface wave analysis polarization phase velocity dispersion curves structure conclusion multiple filtering Gaussian filters constant relative resolution filtering instantaneous period estimation surface wave analysis

10 Kolinsky and Malek: Upper mantle of the Bohemian Massif10 contents motivation data surface wave analysis polarization phase velocity dispersion curves structure conclusion frequency-time spectrogram and truncated fundamental mode spectrogram period (s) velocity (km/s)

11 Kolinsky and Malek: Upper mantle of the Bohemian Massif11 contents motivation data surface wave analysis polarization phase velocity dispersion curves structure conclusion set of harmonic signals

12 Kolinsky and Malek: Upper mantle of the Bohemian Massif12 contents motivation data surface wave analysis polarization phase velocity dispersion curves structure conclusion Kuril Islands continental path 8700 km Scotia Sea oceanic path km particle motion in horizontal plane

13 Kolinsky and Malek: Upper mantle of the Bohemian Massif13 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)

14 Kolinsky and Malek: Upper mantle of the Bohemian Massif14 contents motivation data surface wave analysis polarization phase velocity dispersion curves structure conclusion  s s s T = 50 s T = 100 s T = 150 s

15 Kolinsky and Malek: Upper mantle of the Bohemian Massif15 contents motivation data surface wave analysis polarization phase velocity dispersion curves structure conclusion Love continental Rayleigh continental Love oceanic Rayleigh oceanic group velocity Love PREM Rayleigh PREM

16 Kolinsky and Malek: Upper mantle of the Bohemian Massif16 contents motivation data surface wave analysis polarization phase velocity dispersion curves structure conclusion phase velocity

17 Kolinsky and Malek: Upper mantle of the Bohemian Massif17 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) structure – inversion problem

18 Kolinsky and Malek: Upper mantle of the Bohemian Massif18 contents motivation data surface wave analysis polarization phase velocity dispersion curves structure conclusion - similar dispersion curves may correspond to different velocity models - measured dispersion points can be fitted by different smooth dispersion curves inversion non-uniqueness

19 Kolinsky and Malek: Upper mantle of the Bohemian Massif19 contents motivation data surface wave analysis polarization phase velocity dispersion curves structure conclusion - during Love wave phase velocity inversion we look for v S model - during Rayleigh wave phase velocity inversion we look for v S and v P /v S ratio - depths of interfaces are fixed during the inversion parameters

20 Kolinsky and Malek: Upper mantle of the Bohemian Massif20 contents motivation data surface wave analysis polarization phase velocity dispersion curves structure conclusion inversions

21 Kolinsky and Malek: Upper mantle of the Bohemian Massif21 contents motivation data surface wave analysis polarization phase velocity dispersion curves structure conclusion velocity distribution Z - component R - component T - component

22 Kolinsky and Malek: Upper mantle of the Bohemian Massif22 contents motivation data surface wave analysis polarization phase velocity dispersion curves structure conclusion

23 Kolinsky and Malek: Upper mantle of the Bohemian Massif23 contents motivation data surface wave analysis polarization phase velocity dispersion curves structure conclusion conclusions - 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


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