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Effets of surface topography on seismic ground motion: recent results, remaining issues and needs

AGU09, San Francisco, 17/12/2009 Session S41E - Topography effects in ground motion prediction : From numerical modelling to engineering design. Effets of surface topography on seismic ground motion: recent results, remaining issues and needs. P ierre-Yves BARD (LCPC / LGIT Grenoble)

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Effets of surface topography on seismic ground motion: recent results, remaining issues and needs

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  1. AGU09, San Francisco, 17/12/2009 Session S41E - Topography effects in ground motion prediction : From numerical modelling to engineering design Effets of surface topography on seismic ground motion: recent results, remaining issues and needs Pierre-Yves BARD (LCPC / LGIT Grenoble) Emmanuel CHALJUB (LGIT Grenoble) Bard & Chaljub - AGU2009, December 17, San Francisco, CA

  2. Contents Introduction : conclusions of old reviews New observations New simulations New engineering applications Conclusions • real achievements, but engineering applications still very poor Bard & Chaljub - AGU2009, December 17, San Francisco, CA

  3. Surface topography effects: knowledge status 15-20 years ago Main characteristics • Top amplification (convex part) + foothill deamplification (concave) (for identical soil conditions) • Frequency dependence Maximum effects for l = c/f  mountain width • Largest effects on Horizontal components • T > L >> V (for 2D cases) • Possible range • from 2 to above 10 Origin : not completely captured yet ! • Focusing / defocusing • Reflexion coefficients on side slopes (oblique incidence) • Diffraction and lateral interferences • ??? Fracturation / decompression in summit areas Accounting for them • Codes : nothing in general; a few exceptions however (PS92, EC8, Maximum amplification = 1.4, no frequency dependence) UJF Lectures "Engineering seismology", PYB4, MEEES/STUE/MEMS 2009-2010

  4. New observations • Various kinds • "Classical" • instrumental recordings • observed (heavy) damage • Remote sensing • Spatial variability • Insurance claims Castillon 1887 : x 10 Village Church Church Village (Nechstchein et al., 1995) Bard & Chaljub - AGU2009, December 17, San Francisco, CA

  5. Direct observations Instrumental Site to Reference spectral ratios reference site issue H/V earthquake recordings microtremor recordings Particle motion & directional amplification ? Geophysical surveys very few Damage Hill-tops Castillon – Piène (1887) Rognes (1909) Kozani-Grevena (Greece 1997) CastelNuovo (L'Aquila 2009) (?) (No damage: Tarzana) Cliffs Egion (Greece, 1995) Adames (Greece, 1999) Bard & Chaljub - AGU2009, December 17, San Francisco, CA

  6. Example cliff damage : the Adames area (Athens, 1999) (Gazetas et al., 2002; Assimaki et al., 2005) Bard & Chaljub - AGU2009, December 17, San Francisco, CA

  7. Consistency between observations and theory / numerical estimates Topography effects only Volos (Greece) Epirus (Greece) Kitherion (Greece) Saint-Eynard (France) Rustrel LSBB (France) Other effects Topography + weathering / low velocity Tarzana (California) (??) Ananevo (Kyrgizstan) Adames Egion Not identified Kitherion (Greece) Castillon / Piène (France) Bard & Chaljub - AGU2009, December 17, San Francisco, CA

  8. Kitherion, Greece (Lebrun et al., JOSE 1999) Discrepancy at one site • High frequency only Bard & Chaljub - AGU2009, December 17, San Francisco, CA

  9. Top Particle motion : preferential transverse direction Castillon and Piène (France) Tarzana (California) (Nechstchein et al., 1995) (Spudich et al., 1996) UJF Lectures "Engineering seismology", PYB4, MEEES/STUE/MEMS 2009-2010

  10. Topographic effect and landslide triggering Evidence for larger motion on far side of hill tops from satellite detection of triggered landslides (Papua-New Guinea, Chichi/Taiwan) Meunier et al. EPSL 275 (2008) p.221-232 Meunier et al., 2008 Bard & Chaljub - AGU2009, December 17, San Francisco, CA

  11. UPSAR : San Simeon 2003 + Parkfield 2004 UPSAR array UPSAR array and topography (Wang et al., 2006) Bard & Chaljub - AGU2009, December 17, San Francisco, CA

  12. UPSAR : San Simeon 2003 + Parkfield 2004 and aftershocks Intrinsic variability throughout the array ("intra-event") Comparison with GMPEs: variable inter-event deviation (Wang et al., 2006) Bard & Chaljub - AGU2009, December 17, San Francisco, CA

  13. Evidence from insurance claimsSan Simeon 2003 (see McCrink et al. 2009) Yellow : insurance claim Black dot : insured house (McCrink et al., 2009; Courtesy C. Real) Bard & Chaljub - AGU2009, December 17, San Francisco, CA

  14. New simulations : plenty ! "Isolated" topographies • hill tops • cliffs and canyons • homogeneous and heterogeneous • topography only / topography + geology • Parameter studies Complex topographies • interaction with source (mirroring / shielding) • from DEM to LIDAR data : HF modelling Translational motion + rotational / strains Bard & Chaljub - AGU2009, December 17, San Francisco, CA

  15. Example systematic computations for islated, homogeneous topographies (Nguyen et al., 2007; Gatmiri et al., 2008) Bard & Chaljub - AGU2009, December 17, San Francisco, CA

  16. Example cliff computations Athens / Adames (1999) Aigion (1995) (Athanasopoulos et al., 1999) (Gazetas et al., 2002) Bard & Chaljub - AGU2009, December 17, San Francisco, CA

  17. Complex topography and scattering / variability LA area (Ma et al., 2007) (PGVtopo – PGVnotopo)/PGVnotopo Without topography With topography Bard & Chaljub - AGU2009, December 17, San Francisco, CA

  18. Another situation (Taiwan / Taipei basin) 100 x (PGVtopo – PGVnotopo)/PGVnotopo h = 15 km h = 2 km h = 40 km Point source in the I-lan area (East) Lee et al., 2009a Bard & Chaljub - AGU2009, December 17, San Francisco, CA

  19. From standard DEM to LIDAR standard 40m DEM pga maps LIDAR Yangminshan area (Taiwan) Lee et al., 2009b Bard & Chaljub - AGU2009, December 17, San Francisco, CA

  20. From flat to LIDAR Lee et al., 2009b Bard & Chaljub - AGU2009, December 17, San Francisco, CA

  21. New engineering applications Building codes : what's new ? • LITTLE / NOTHING (EC8 + ?) • A few simple proposals however for cliffs • (Gazetas et al., Bouckovalas et al., … : amplification factor + area width) • ? Too complex ? • Frequency dependence • Coupling geology / topography Other • Landslide hazard in mountainous areas • ? Consistency with use of slope as a proxy to VS30 ? Bard & Chaljub - AGU2009, December 17, San Francisco, CA

  22. Surface topography effects : summary of results Time domain: Amplification of peak values Frequency domain : Peak spectral amplification PGVH top / PGVH base Top / base Fourier spectral ratio Shape ratio h/l Shape ratio h/l UJF Lectures "Engineering seismology", PYB4, MEEES/STUE/MEMS 2009-2010

  23. Proposals for engineering applications Homogeneous cliffs • Amplification factors • + area width • (Bouckovalas et al., 2005) • Heterogeneous cliffs • (Assimaki et al., 2005) • More parameters … (Bouckovalas et al., 2005) Bard & Chaljub - AGU2009, December 17, San Francisco, CA

  24. With topographic amplification Without topographic amplif. Estimation of increase in landslide hazard • Methodology : • Newmark analysis for slide detection (source) from yield acceleration ag • runout for deposit areas • Area : Baishiya area, Nantou, Taiwan (Peng et al., 2009) Bard & Chaljub - AGU2009, December 17, San Francisco, CA

  25. Conclusions Additional consistent evidence of amplification • convex parts : hill-tops and cliffs • mixed with geological / lithological effects • especially at high frequencies + Diffraction / scattering effects • increased variability ? Larger s for GMPE in mountainous areas ? • significant strains (upper bounds from displacements and Rayleigh velocity) Still (most) missing and welcome • Dense array recordings coupled with detailed geophysical surveys • HF issue : short wavelength characterization at shallow depth • convincing statistics for building codes • ? effects of strains on landslide triggering Bard & Chaljub - AGU2009, December 17, San Francisco, CA

  26. References 1 Assimaki D., Gazetas G., and Kausel E., 2005, BSSA, 95-3, 1059-1089. Athanasopoulos, G.A., P.C. Pelekis and E.A. Leonidou, 1999. SDEE 18, 135-149 Bouckovalas, G.D. and A. G. Papadimitriou, 2005. SDEE 25, 547–558 Chaljub, E., P. Moczo, S. Tsuno, P.-Y. Bard, J. Kristek, M. Käser, M. Stupazziniand M. Kristekova, 2010. BSSA, in press. Chavez-Garcia, F.J., Sanchez, L.R. and Hatzfeld, D., 1996, BSSA. 86, 1559–1573. Gatmiri B, Nguyen KV, 2007. SDEE 27, 183–8. Gazetas, G., P. V. Kallou, and P. N. Psarropoulos, 2002. Nat. Haz. 27-1-2, 133–169 Grazer, V., 2009. SDEE 29, 324– 332 Havenith, H.B, D. Jongmans, E. Faccioli, K. Abdrakhmatov and P.-Y. Bard, 2002. BSSA, 92-8, 3190-3209. Lebrun, B., D. Hatzfeld, P.-Y. Bard and M. Bouchon, 1999. JOSE, 3-1, 1-15. Lee, S-J, D. Komatitsch, B-S Huang, and J. Tromp, 2009. BSSA, 99-1, 314–325. Lee, S-J, Y-C Chan, D. Komatitsch, B-S Huang, and J. Tromp, 2009. BSSA, 99-2A, 681–693. Bard & Chaljub - AGU2009, December 17, San Francisco, CA

  27. References 2 Ma, S., R. J. Archuleta, and M. T. Page, 2007. BSSA 97, 2066–2079, Maufroy, E., V.M. Cruz-Atienza, S. Operto, O. Sardou, G. Sénéchal, M. Dietrich, and S. Gaffet, 2008. Paper 02-0188, 14WCEE, Beijing, China. McCrink, Timothy P., Chris J. Wills, Charles R. Real, and Michael W. Manson, 2009. Submitted to Earthquake Spectra. Meunier, P. N. Hovius, and J. A. Haines, 2008. EPSL 275, 221–232. Nechtschein S., Bard, P.Y., Gariel, J.C., Mèneroud, J.P., Dervin, P., Cushing, M., Gaubert, C., Vidal, S. and Duval, A.M., 1995, 5ICSZ, Nice (France), 1067–1074. Pedersen, H., B. Le Brun, D. Hatzfeld, M. Campillo and P.-Y. Bard, 1994. BSSA, 84, 1786-1800. Peng, W.-F., C-L Wang, S-T Chen, S-T Lee, 2009. Computers & Geosciences 35, 946–966 Spudich, P., Hellweg, M. and Lee, W.H.K., 1996, BSSA, 86, S193–S208. Wang, G-Q, G-Qi Tang, C R. Jackson, X-Y Zhou, and Q-L Lin, 2006. BSSA, 96-4B, S159–S182. Bard & Chaljub - AGU2009, December 17, San Francisco, CA

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