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SISMOVALP WP6 Alpine ground motion

SISMOVALP WP6 Alpine ground motion. Numerical benchmark of ground motion simulation in the Grenoble valley Description and first results . ESG2006 Numerical benchmark. Numerical Benchmark of 3D ground motion simulation in the Grenoble Valley : Description and First Results.

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SISMOVALP WP6 Alpine ground motion

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  1. SISMOVALP WP6Alpine ground motion Numerical benchmark of ground motion simulation in the Grenoble valley Description and first results Sismovalp final meeting, Martigny, 02/10/2006

  2. ESG2006 Numerical benchmark Sismovalp final meeting, Martigny, 02/10/2006

  3. Numerical Benchmark of 3D ground motion simulation in the Grenoble Valley : Description and First Results Emmanuel Chaljub, Seiji Tsuno, François Thouvenot, Michel Dietrich, Pierre-Yves Bard + many colleagues & predictors Sismovalp final meeting, Martigny, 02/10/2006

  4. Overview • Introduction • Background Data • Tectonic context / Seismicity (F. Thouvenot) • Geophysical and geotechnical data (M. Dietrich) • General description and first results (E. Chaljub) • Description of the benchmark : model and events • Participation / Methods • Outline of the Grenoble basin seismic response • Detailed comparisons (S. Tsuno) • Addressed topics and comparison methods • Example results • Preliminary Conclusions • Recap / Lessons / Benchmark Future Sismovalp final meeting, Martigny, 02/10/2006

  5. Proposed predictions "Imposed" • 2 weak motion events • W1, W2 • 2 strong motion events • S1, S2 • Extension of W1, W2 to stronger events • Source : imposed geometry and kinematics • + "Free-style" • M6 (S1) : Estimate + uncertainties • (NL, source variabilities) Sismovalp final meeting, Martigny, 02/10/2006

  6. Material provided to participants : topographies Bedrock / sediment interface: 250 m gridstep Surface : 50 m gridstep Sismovalp final meeting, Martigny, 02/10/2006

  7. Basin No shallow structure Qs = 50 Bedrock Vsurf= 3200 m/s Qs = ∞ Material provided to participants : velocity model Stiff sediments but very hard bedrock : strong impedance contrast Sismovalp final meeting, Martigny, 02/10/2006

  8. Material provided to participants: source parameters Sismovalp final meeting, Martigny, 02/10/2006

  9. Material provided to participants : recordings Borehole, at depth Borehole, surface  anchor deterministic calculations  empirical Green's functions Sismovalp final meeting, Martigny, 02/10/2006

  10. Material NOT PROVIDED • Input motion for 1D and 2D calculations Sismovalp final meeting, Martigny, 02/10/2006

  11. Results requested from participants : 1D case • Time series (at least 30 s) of ground velocity at 1 station (borehole surface) Sismovalp final meeting, Martigny, 02/10/2006

  12. Results requested from participants : 2D methods • Time series (at least 30 s) of ground velocity along a cross-section (10 stations, through borehole) Sismovalp final meeting, Martigny, 02/10/2006

  13. Results requested from participants : 3D case • Time series (at least 30 s) of ground velocity for 40 stations) • + PGV map Sismovalp final meeting, Martigny, 02/10/2006

  14. Results requested from participants : EMP methods • Time series (at least 30 s) of ground velocity for 3 stations (including borehole) Sismovalp final meeting, Martigny, 02/10/2006

  15. Results received Sismovalp final meeting, Martigny, 02/10/2006

  16. Results received : details Sismovalp final meeting, Martigny, 02/10/2006

  17. Participation 1D Contribution to Numerical benchmark 2D EM 3D Frequency (Hz) Frequency band analyzed

  18. Addressed topics 1. Overall variability (S1 case at Borehole site) Each method; 1D, 2D, 3D Flat, 3D Topo., EGF -> Waveform, Input motion -> Fourier spectra, Spectral ratio -> Non-linear (1D, 2D) & Topography effects (3T) 2. Comparison method -> Waveform, Maximum values (PGV) -> Fourier spectra, Spectral ratio, Resonance peak 3. Applying misfit criteria to 3D estimations (S1 case) -> Anderson’s method -> Kristekova’s method 4. Additional learnings -> from S2 -> from W1/W2, match with observation ?

  19. Overall raw variability – Time domain Surface (GL) Input (GL -541.5m) 1D 1D 2D 2D EM EM 3F 3F 3T 3T Velocity Waveform at bore-hole site (OGFB & OGFH)

  20. Comparison - Spectra Two groups Fourier spectra at borehole site (OGFB & OGFH)

  21. Comparison - Spectral ratio 1D 2D 1D, 2D, EM, 3D and 3T 3D EM Spectral ratio at bore-hole site

  22. 3D Flat Simulation- case S1 OGFH OGFB N Bedrock depth of Grenoble basin

  23. Spectra - 3D Flat & case S1 Fourier Spectra at OGFB (Gl -541.5m) Fourier Spectra at OGFH (GL)

  24. Spectral ratio - 3D Flat & case S1 Spectral ratio at borehole site

  25. Spectral ratio - 3D Topo. & case S1 Spectral ratio at borehole site

  26. Example results : PGV map Sismovalp final meeting, Martigny, 02/10/2006

  27. S1 case : 3D, Flat predictions Sismovalp final meeting, Martigny, 02/10/2006

  28. Conclusion Predicted waveforms and Fourier spectra exhibit a large (too large, huge, unacceptable ?) variability. Peak ground velocities on surface also exhibit a significant variability due to the differences in investigated frequency ranges. BUT Spectral ratios at bore-hole site are relatively stable, specially for the resonance frequency. Differences in “Input motion” (i.e., source modelling) have the largest influence for the numerical simulations in this benchmark test.

  29. Main learnings 1 • Difficulties of the exercise • Data and model format : to be standardized • HF / Short wavelength structure • Utility / absolute necessity of imposed exercises • Simpler cases • Consistency 1D / 2D / 3D : input motion • Simple for incident plane waves • ? Including source ? • EGF : bad S/N ratio at low frequencies • Timing too tight • Plan more time for predictions  start earlier ! • 2 years / 18 months / 9 months Sismovalp final meeting, Martigny, 02/10/2006

  30. Main learnings 2 • Outcomes • Large variability in input motion, significantly less in site response • Consistency of 2D – 3D modelling (amplification levels / frequency) • (Very) Encouraging results for different 3D models • Topography effects • Use of misfit criteria • Definitely useful for objectively quantifying similarity / dissimilarity, but not yet enough practice • Anderson's criteria more robust and engineering –oriented • Kristekova's : for already rather similar signals • Need for looking at time histories, spectra, and spectral ratios Sismovalp final meeting, Martigny, 02/10/2006

  31. Example comparison after iteration (and bug correction) Sismovalp final meeting, Martigny, 02/10/2006

  32. Main learning • 3D modelling is not yet "press-button" • Too fast applications may yield very wrong results (and large untrust from end-users) • BUT very similar results are possible event with completely different numerical schemes • (probably indicative of the "exact" solution) • Conditions for careful use • well-validated techniques & codes • Well trained users • Careful model implementation • External review Sismovalp final meeting, Martigny, 02/10/2006

  33. Future of the Grenoble basin benchmark • Short term • Summary report for Proceedings Volume 2 • Not all results for all receivers • Focusing on some specific aspects • Intermediate term • ? Second round for converging ? • First results VERY ENCOURAGING  ? Sismovalp extension ? • Other aspects • Other receivers • Wavefield (array) • NL effects (2D) • SPICE (2?) • ? Part of a collection of real sites for benchmarking • Long term • Shallow structure and HF / BB response : deterministic or stochastic ? Sismovalp final meeting, Martigny, 02/10/2006

  34. Acknowledgments Sismovalp final meeting, Martigny, 02/10/2006

  35. Acknowledgements F. Anselmetti, C. Beck, C. Bordes, M. Campillo,E. Chapron, J. Converset, C. Cornou, F. Cotton, M. De Batist, P. Finckh, E. Flavigny, P. Foray, J.F Gamond, S. Garambois, J.R. Grasso, J.P Gratier, P. Guéguen, R. Guiguet, S. Hatton, L. Jenatton, J. Jerram, S. Labanieh, B. Lebrun, F. Lemeille, G. Menard, O. Méric,G. Nicoud, S. Roussel, P. Roux, L. Stehly, S. Tadenuma, M. Vallon , P. Van Rensbergen, J. Verbeke, C. Voisin Sismovalp final meeting, Martigny, 02/10/2006

  36. ESG2006 Contributions relative to alpine valleys • Predictions : Sxx • Characteristics of Grenoble Valley • Similar cases : Alpine Valleys Sismovalp final meeting, Martigny, 02/10/2006

  37. Prediction Posters S01 Numerical Simulation of Wave Propagation in the Grenoble Basin H. Aochi, J. Rey and J. Douglas S02 1D and 2D linear and nonlinear site response in the Grenoble area L.F. Bonilla, S. Nielsen and P.C. Liu S03 A ground-motion simulation approach coupling rock groundmotion prediction equations and the empirical Green's functions method M. Causse, F. Cotton and C. Cornou S04 Spectral element modeling of 3D wave propagation in the alpine valley of Grenoble, France E.Chaljub   S05 Numerical Benchmark of 3D Ground Motion Simulation in the Valley of Grenoble, French Alps H. J. Chiang, T. M. Chang and K. L. Wen S06 Site effects in a deep alpine valley for various seismic sources N. Delépine and J.-F. Semblat S08 An Efficient Ader-Dg Method for 3-Dimensional Seismic Wave Propagation in Media With Complex Geometry M. Käser, M. Dumbser and J. De La Puente S09 Ground Motion Simulation of two Moderate Size Earthquakes in the Grenoble Area using Summation of Small Earthquakes C. Kohrs-Sansorny, F. Courboulex and A. Deschamps S10 Ground motion simulation on a 2D profile across the Grenoble basin using the Aki-Larner discrete wave-number method C. Lacave and F. Hollender S12 Modeling of strong earthquake motion in the Grenoble Valley, French Alps P.Moczo et al. S14 Kinematic composite souce model combined with EGF for modeling strong ground motion Application to the Grenoble Basin J. Ruiz, D. Baumont, P. Bernard and C. Berge- Thierry S15 3D Ground Motion Simulation of the Grenoble valley by GeoELSE Marco Stupazzini S30 Kinematic modeling of strong earthquake motion in the Grenoble Valley, French Alps P. Franek and F. Gallovic   Sismovalp final meeting, Martigny, 02/10/2006

  38. Grenoble Valley S16 Seismicity of the Grenoble Area F. Thouvenot, L. Jenatton and R. Guiguet S17 High-amplitude reflections in proglacial lacustrine basin fills of the NW Alps : Origin and Paleoenvironment Implications E. Chapron, M. Dietrich, C. Beck, P. Van Rensbergen, G. Menard, P. Finckh, G. Nicoud, F. Lemeille, F. Anselmetti and M. De Batist S18 Seismic profiling and borehole measurements in the Isère valley near Grenoble, France: 1 data acquisition and processing M .Dietrich, C. Cornou, G. Ménard, F. Lemeille, F. Guyoton and R. Guiguet S19 Seismic profiling and borehole measurements in the Isère valley near Grenoble, France 2 Interpretation G. Ménard, M.Dietrich, M. Vallon , S. Tadenuma, C. Bordes, O. Méric and F. Lemeille 126 S23 Measurement and variability study of site effects in the 3D glacial valley of Grenoble, French Alps E. Chaljub, C. Cornou, J. Verbeke, J. Converset, C. Voisin, L. Stehly, J.R. Grasso, P. Guéguen, S. Roussel, P. Roux, S. Hatton and M. Campillo S24 Characterising the non linearities of the lacustrine clays in the Grenoble basin J. Jerram, P. Foray, E. Flavigny and S. Labanieh S25 Geotechnical, geophysical and seismological data used for the estimate of the highest amplified frequency in the basin of Grenoble P. Guéguen, S. Garambois, S. Tadenuma, B. Lebrun, and F. Cotton Sismovalp final meeting, Martigny, 02/10/2006

  39. Alpine Valleys S26 Sites effects in the Vallorcine valley C. Voisin, P. Guéguen, J.R. Grasso, C. Gomes S27 Modelling of strong ground in the July 2004, Mw 5.2 Bovec earthquake M. Vanini, M. Villani, E. Faccioli and A. Gosar S28 Seismic Response Analysis of La Salle Fluvial Fan (Valle D' Aosta Italy) C. Turino, G. Ferretti, C. Eva, C. Gauzzi and R. Paolucci Sismovalp final meeting, Martigny, 02/10/2006

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