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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

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

esg2006 numerical benchmark

ESG2006 Numerical benchmark

Sismovalp final meeting, Martigny, 02/10/2006

slide3

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

overview
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

proposed predictions
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

material provided to participants topographies
Material provided to participants : topographies

Bedrock / sediment interface: 250 m gridstep

Surface : 50 m gridstep

Sismovalp final meeting, Martigny, 02/10/2006

material provided to participants velocity model
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

material provided to participants source parameters
Material provided to participants: source parameters

Sismovalp final meeting, Martigny, 02/10/2006

material provided to participants recordings
Material provided to participants : recordings

Borehole, at depth

Borehole, surface

 anchor deterministic calculations

 empirical Green's functions

Sismovalp final meeting, Martigny, 02/10/2006

material not provided
Material NOT PROVIDED
  • Input motion for 1D and 2D calculations

Sismovalp final meeting, Martigny, 02/10/2006

results requested from participants 1d case
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

results requested from participants 2d methods
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

results requested from participants 3d case
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

results requested from participants emp methods
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

results received
Results received

Sismovalp final meeting, Martigny, 02/10/2006

results received details
Results received : details

Sismovalp final meeting, Martigny, 02/10/2006

participation
Participation

1D

Contribution to Numerical benchmark

2D

EM

3D

Frequency (Hz)

Frequency band analyzed

addressed topics
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 ?

overall raw variability time domain
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)

comparison spectra
Comparison - Spectra

Two groups

Fourier spectra at borehole site (OGFB & OGFH)

comparison spectral ratio
Comparison - Spectral ratio

1D

2D

1D, 2D, EM, 3D and 3T

3D

EM

Spectral ratio at bore-hole site

3d flat simulation case s1
3D Flat Simulation- case S1

OGFH

OGFB

N

Bedrock depth of Grenoble basin

spectra 3d flat case s1
Spectra - 3D Flat & case S1

Fourier Spectra at OGFB (Gl -541.5m)

Fourier Spectra at OGFH (GL)

spectral ratio 3d flat case s1
Spectral ratio - 3D Flat & case S1

Spectral ratio at borehole site

spectral ratio 3d topo case s1
Spectral ratio - 3D Topo. & case S1

Spectral ratio at borehole site

example results pgv map
Example results : PGV map

Sismovalp final meeting, Martigny, 02/10/2006

s1 case 3d flat predictions
S1 case : 3D, Flat predictions

Sismovalp final meeting, Martigny, 02/10/2006

conclusion
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.

main learnings 1
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

main learnings 2
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

example comparison after iteration and bug correction
Example comparison after iteration (and bug correction)

Sismovalp final meeting, Martigny, 02/10/2006

main learning
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

future of the grenoble basin benchmark
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

acknowledgments
Acknowledgments

Sismovalp final meeting, Martigny, 02/10/2006

acknowledgements
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

esg2006 contributions relative to alpine valleys
ESG2006 Contributions relative to alpine valleys
  • Predictions : Sxx
  • Characteristics of Grenoble Valley
  • Similar cases : Alpine Valleys

Sismovalp final meeting, Martigny, 02/10/2006

prediction posters
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

grenoble valley
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

alpine valleys
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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