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Correlation and Scaling of P and S Anomalies in D" Beneath Central America and Pacific

Correlation and Scaling of P and S Anomalies in D" Beneath Central America and Pacific. Xiaodong Song Department of Geology University of Illinois at Urbana-Champaign August 7, 2007 2 nd VLAB Workshop University of Minnesota.

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Correlation and Scaling of P and S Anomalies in D" Beneath Central America and Pacific

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  1. Correlation and Scaling of P and S Anomalies in D" Beneath Central America and Pacific Xiaodong Song Department of Geology University of Illinois at Urbana-Champaign August 7, 2007 2nd VLAB Workshop University of Minnesota Collaborators: Xinlei Sun, Sihua Zheng, Don Helmberger, and Steve Grand

  2. Rs/p=d(lnVs)/d(lnVp) Rp/s=d(lnVp)/d(lnVs) Rpho/s Elastic parameters of MgSiO3 ppv (Wentzcovitch et al. PNAS 2006) Mineral physics diagram with seismic parameters (Karato and Karki JGR 2001)

  3. Grand 2002 Karason and van der Hilst 200 Tkalcic et al. 2002 Lay et al. 1998

  4. Direct comparison of P and S tomographic models is difficult • Sampling, resolution, and damping are quite different. • S resolution is considerably better. PcP is a poor reference phase. PdP is rare. • P and S correlation becomes poor in lowermost mantle (Robertson and Woodhouse 1996; Kennett 1998; Masters et al. 2000)

  5. PKP ray paths Example seismograms Sun, Song, Zheng, and Helmberger, PNAS 2007

  6. Sensitivity of PKP differential AB-DF differential times to mantle heterogeneities

  7. Observed PKP residuals plottted at CMB (with Grand’s model)

  8. Azimuthal variation

  9. Event 1: Mar. 15, 2001, 32.32oS, 71.49oW, 37 km, mb 5.6 Event 2: Sept. 24, 2002, 31.52oS, 69.20oW, 119 km, mb 6.2

  10. Correlation between observed residuals and predictions

  11. Distributions of predicted residauls AB-DF vs DF, whole mantle AB-DF vs AB, whole mantle AB-DF source side vs station side

  12. P-velocity model of this study

  13. P model at D” and observed residuals

  14. P perturbations along 3 profiles across the Cocos Boundary

  15. along 3 profiles along latitude

  16. Map of cross-correlation coefficients

  17. PKP data sampling the Pacific from S. America earthquakes to Chinese stations Zheng, Sun, and Song, Chinese J Geophys 2007

  18. Slope=0.359 +/- 0.040 Data and Grand’s predictions

  19. Grand’s data: ScS residuals plotted at CMB bounce points (distance > 45 deg).

  20. Grand’s ScS-S data and model predictions

  21. Summary Contrary to some previous studies, P and S perturbations correlate well beneath Central America and parts of Central Pacific. R values are significantly different for the two regions. It is estimated about 1.95 +/- 0.09 for Central America and about 3.30+/-0.36 for Central Pacific.

  22. Vk2(dVk/Vk)=(Vp2/R-4/3*Vs2)(dVs/Vs), where R=Rs/p=(dVs/Vs)/(dVp/Vp) If R> Vp2/(4/3*Vs2) or about 2.6 to 2.7 in D”, bulk sound perturbation is anti-correlated with shear wave perturbation.

  23. Work in progress … ScS-S SKS-S PKP (AB-DF)

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