QSHA, Réunion du 01/06/2007 1

Projet QSHA – WP3

Laboratoire Central des Ponts et Chaussées

58, bd Lefebvre, 75732 Paris Cedex 15

http://www.lcpc.fr

Réunion du 01/06/2007

QSHA, Réunion du 01/06/2007 2

WP3 - Ground motion simulation

QSHA, Réunion du 01/06/2007 3

WP3-1 Methological improvements

Main goals :• main features of the various methods (table)• current or potential improvements• range of application (frequency, heterogeneity,

non linearity…)• comparisons (misfit criteria) :

– efficiency– accuracy– stability…

• very simple canonical models with well constrained features (and simple sources)

Developments of numerical tools for wave propagation

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Fiche descriptive / méthode• Type/name of method: FVTD - Finite-Volume Method in the Time Domain• Contributors (labs): N. Glinsky-Olivier (Cermics/INRIA), S. Lanteri (INRIA), M.

Benjemaa (INRIA), S. Piperno (Cermics/INRIA), J. Virieux (GeoSciences Azur),• Basic principle & improvements:

– Principles : Finite Volumes, Unstructured grids, Centered numerical fluxes, Leap-frog time-scheme, Energy conservation, Weak treatment of boundary conditions (free surface, ABC, dynamic rupture)

– Improvements : extension using Discontinuous Galerkin Finite Elements, parallel solver in development

• Features:– Source/propagation (S, P, S+P): S+P– Coupled methods: coupling with PML, poss. coupling with FETD & FDTD meth– 1D/2D/2.5D/3D : 2D (3D parallel solver under development)– Time/frequency: time-domain– Direct/iterative: direct (explicit in time)– Elements size (fraction of ): 1/12 in FVTD (less in DGTD)– Model size (nb of ): – Free-surface topography: Yes– Heterogeneity: Yes– Anisotropy: Yes (future)– Material behav. (lin., NL, eq.lin): linear– Damping (NCQ, rheol.): none (possible)– Main references

à remplirpour S3 !!

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Tableau récapitulatif méthodes

Groups FDM FEM SEM FVM BEM DEM EGF

GEOAZUR L L NL

LGIT L/(NL) NL

BRGM L L/EQ/NL

NL NL

CEA ? L/NL ?

LCPC L/EQ/NL

L/NL L NL

L=linear, EQ=equivalent linear, NL="non-linear"

à compléter/corriger…!

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Simple canonical models• Simple canyons/basins :

– 2D (SismoValp) : 1 asymmetrical models + higher frequencies… is it useful to choose other 2D models ?

– 3D (mainly semi-spherical, asymmetric)

• Simple sources (plane waves, points sources…)

• Analyze efficiency/accuracy taking into account :

– Damping/attenuation,

– Discretization, geometrical extent...

– Constitutive laws

– Simple stratification,

– …

• Possible link with/contribution to Spice database (http://www.nuquake.eu/SPICECVal) choice among existing models

in the database ?!

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WP3-2 Sensitivity studies (P-Y Bard)

• Key parameters in modelling :– intermediate canonical models (for sensitivity analyses)– influence of topography description– sensitivity to source location, source dynamics, source

extension…– influence of soil non linearities in 2D and 3D– influence of the physical model (variability) on response

spectra (input uncertainties vs output uncertainties)

• identification of the key parameters to be measured

• finally, empirical description of the physical effects from theoretical results(e.g. 2D/3D aggravation factor...)

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WP3-2 Sensitivity studies (P-Y Bard)

(Nearly) realistic models :• Nice (WP1 : test de rugosité d’interface…)• Grenoble > modèle avec gradient

+ modèle à couches (pour BEM !)• Algiers• Naples…

…cf WP3-3 & WP3-4

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WP3-3-WP3-4 Benchmarking (E.Chajlub/E.Foerster)

• Validation of developed codes based on international benchmark but not tied to ESG2006 with two geometries (Basins and margins)

• Simulations performed in the Nice zone including water layer

• Fully realistic models...

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WP3-5 Statistical comparison(Hideo Aochi)

• Variability of simulations using intensive simulations

related to model variations

related to source variations

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WP 3-6 Lessons (J.Virieux)

• To be done in S5 and S6 (2008) when comparing methods

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WP 3-X ...

Rapport S3 : contributions à envoyer à semblat@lcpc.fr(y compris "fiche de synthèse"pour chaque méthode)

Prochaine réunion :2 ou 3 juillet 2007(avant Colloque AFPS)