Seiscope

SEISCOPE is a research project dedicated to the development and application of high-resolution imaging methods of the subsurface, at various scales, ranging from the near surface (a few meters deep) to the deep crust (several tens of kilometers). These methods are mainly based on the inversion of complete seismic waveforms (Full Waveform Inversion). The goal is to determine the mechanical properties of the studied medium (e.g. P and S wave velocity, density, anisotropic attenuation). The methodology used is based on an iterative inversion scheme where seismic wave propagation is modeled from an initial model. The comparison between the modeled signals and the observed seismic data allows the calculation of a cost function. The medium parameters are modified at each iteration in order to minimize it.

This research theme is at the interface of several disciplinary fields and requires expertise in geophysics, applied mathematics as well as high-performance computing (HPC).

Currently, SEISCOPE mainly develops two Fortran computing codes using two different physics formalisms of wave propagation, each being approached with a different numerical scheme. The first code, TOYxDAC_TIME, is a finite difference code based on a visco-acoustic formalism. The second code, SEM46, is a spectral finite element code allowing an acoustic, acoustic-visco-elastic or visco-elastic formalism. The two codes have respectively three and two levels of parallelization (MPI/MPI and OpenMP standards for TOYxDAC_TIME and MPI/MPI for SEM46) making it possible to solve 3D problems where several tens of millions of degrees of freedom are calculated. These codes run on local and national calculation platforms. In recent years, the volume of hours granted by GENCI (Grand Équipement National de Calcul Intensif) to the SEISCOPE project has represented on average 5 million scalar hours with an increasing trend.