Offre de post-doctorat en calcul haute performance pour la sismique 3D – Pau

Offre de post-doctorat Post-doc en calcul haute performance pour la sismique 3D / Post-doc located at INRIA/Pau University in « High Performance Computing for fluid/solid coupling. Application to the 3D modeling of seismic waves propagation at high scales »

– Type d’offre : Post-doctorant
– Lieu de travail : Pau (64)
– Thème de recherche : STIC sciences de la vie et de l’environnement
– Projet : MAGIQUE – Responsable scientifique : julien.diaz – at – inria.fr, roland.martin – at – get.obs-mip.fr – Contact RH : cyril.gerboin – at – inria.fr – – – Date limite de candidature : 29/06/2012
– A propos d’Inria et du poste :  The topic of the post-doc is linked with the scientific priority « Modeling, Programming, Communicating and Interacting », and in particular « Modeling, Simulation and Optimization of Complex Dynamic Systems », since we wish to obtain a better modeling of the Earth crust in order to simulate the propagation of seismic waves with a higher accuracy.
– Mission : The topic of this post-doc is a part of a research programm entitled « High Performance Computing for the numerical 3D modelling of Earth crust by seismic and gravimetry ». This programm aims at improving the modeling of the subsurface of the Earth by taking into account the rotation of the Earth, its gravity field, the viscoelasticity, the Oceans and the bathymetry. One of the main axis of the project is the modelling of wave propagation for the improvement of seismic imaging and of earthquakes simulations. We propose to design and to implement a finite element method for coupling elastodynamic and acoustic wave equations, which could accurately describe the transmission phenomena occuring at the interfaces between the surface. This is crucial in order to model seismic wave propagation between oceanic and continental crusts, but also in order to improve offshore seismic imaging. The numerical method will be implemented in two 3D High Performance Computing codes. The first one, SPECFEM, is based on spectral element method and is widely used in the geophysical community. The second one, Hou10ni, is based on a Discontinuous Galerkin method and is developed by Magique 3D. It should be soon released under a CeCill License. The codes will be used to model major earthquakes, such as Sumatra and Japan 2011. This work will be made in collaboration with Roland Martin (Research Engineer at Observatoire Midi-Pyrénées, Laboratory GET of CNRS at Toulouse University) and Dimitri Komatitsch (Laboratory of Acoustics and Mechanics, CNRS, Marseille) for the SPECFEM aspects of acoustic-elastic coupling and for massively parallel porting of the different codes on GENCI, french mesocenters and international PRACE OpenMP/MPI clusters.
– Descriptif du poste : During the first part of the project, the post-doctoral researcher will design the numerical method for fluid-structure coupling. Since the depth of the ocean is very thin compared with the size of the earth, the mesh will be composed of very fine cells in the water. This will severely impact the stability condition of the time scheme and it will be necessary to consider a local time stepping method, such as the one proposed in [Madec, Diaz] for two-dimensional problems, in order to have two different time steps in the two media. The first step will be to consider the extension of this method to three-dimensional problems, which is not trivial, and to perform a numerical analysis of the method. The second step will be the improvement of the accuracy of the algorithm, which is only of second order in time. It will consists in designing and analyzing a high-order local-time stepping algorithm. The post-doctoral researcher will also have to get familiar with the codes SPECFEM and Hou10ni. Once this first part is achieved, we will consider the parallelization of the methods in a HPC framework. The main difficulty will be the load balancing between the computations in the earth, in the ocean and at the interface since fluid structure algorithm requires the solution to a linear system at the interface between the two media. The last part of the post-doctoral project will be dedicated to the validation of the codes and to the simulation of the major earthquakes of Sumatra, Fukushima and Concepcion.
– Profil recherché : The postdoctoral researcher should have a PhD. In Applied Mathematics. He, or she, should have experience in finite element methods for partial differential equations. He, or she, should have excellent programming skills (preferably in FORTRAN 90 or higher) and a good knowledge of parallel computing (MPI and/or OpenMP). Experience in wave propagation simulation and/or large linear system solvers and/or physics and geophysics would be an advantage.
– Duration : 16 months – Monthly salary after taxes around 2 130 ? (medical insurance included)
– Informations complémentaires : In the interests of protecting its scientific and technological assets, INRIA is a restricted-access establishment. Consequently, it observes special regulations for welcoming foreign visitors from outside of the Schengen area. The final acceptance of each candidate thus depends on applying this security and defence procedure.
– Ronan Madec ; Dimitri Komatitsch ; Julien Diaz. Energy-conserving local time stepping based on high-order finite elements for seismic wave propagation across a fluid-solid interface. Computer Modeling in Engineering and Sciences, Tech Science Press, 2009, 49 (2), pp. 163-189.
– Peter, D., Komatitsch, D., Luo, Y., Martin, R., Le Goff, N., Casarotti, E., Le Loher, P., Magnoni, F., Liu, Q., Blitz, C., Nissen-Meyer, T., Basini, P. and Tromp, J. (2011), Forward and adjoint simulations of seismic wave propagation on fully unstructured hexahedral meshes. Geophysical Journal International, Vol. 186, pp. 721-739
– Roland Martin, Dimitri Komatitsch and Stephen D. Gedney. A variational formulation of a stabilized unsplit convolutional perfectly matched layer for the isotropic or anisotropic seismic wave equation, Computer Modeling in Engineering and Sciences, vol.37, No.3, pp.274-304, 2008.
– Dimitri Komatitsch, Christophe Barnes and Jeroen Tromp, Wave propagation near a fluid-solid interface : a spectral element approach, Geophysics, vol. 65, p. 623-631 (2000).
– Julien Diaz ; Patrick Joly, A time domain analysis of PML models in acoustics. Computer Methods in Applied Mechanics and Engineering, Elsevier, 2006, 195 (29-32), pp. 3820-3853
– Calendrier campagne 2012 – 16 janvier 2012 : Début – 29 juin 2012 : Fin – Fin mars : Première période de sélection – Fin juin-début juillet : Deuxième période de sélection
– A compter du 15 octobre 2012 : Prise de fonction
– Conditions pour postuler – La thèse devra avoir été soutenue en 2011 ou 2012. Dans le cas où la thèse n’était pas soutenue au moment de la candidature, la date de soutenance et le jury devront être indiqués explicitement.
– Les postes sont consacrés aux thèmes prioritaires de recherche de l’institut. Toutefois des candidatures de haut niveau sur des sujets non-prioritaires seront également examinées.
– Une attention particulière sera accordée aux candidats français et étrangers ayant préparé leur thèse à l’étranger, mais toute candidature de haut niveau sera étudiée avec soin.
– Aucune condition de nationalité.
– Si vous avez passé votre thèse au sein d’un centre de recherche Inria, vous ne pouvez postuler sur ce centre.
– Les pièces des dossiers de candidature : un CV, la liste des publications accompagnée des deux publications jugées les plus représentatives, une lettre de motivation, une ou des lettres de recommandation, une perspective d’insertion professionnelle après le post-doctorat.
– Le lieu d’affectation du post-doctorat doit être distinct de celui où la thèse a été conduite. Cette condition ne s’applique pas aux candidats disposant d’une RQTH ou d’une carte d’invalidité.

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