PhD opportunities

New seismic imaging approaches for the subsurface characterisation

Thesis proposal

Area of expertiseGosciences et goingnierie
Doctoral SchoolGRNE - Gosciences, Ressources Naturelles et Environnement
SupervisorM. Herv CHAURIS
Research unitGeosciences
ContactCHAURIS Herv
Keywords., .
AbstractSeismic imaging aims at determining the subsurface structures, for example P-wave velocity models, from seismic data usually acquired at the surface. For quantitative images, the standard approach is to solve iteratively the inverse problem. Recently and in parallel, three groups (Shell, The Netherlands ; University of Houston, USA ; and MINES ParisTech, France) proposed a direct solution for the inverse problem, instead of an iterative resolution (ten Kroode, 2012 ; Hou and Symes, 2015 ; Chauris and Cocher, 2017). Quantitative properties can be obtained within a single iteration. Only few persons thought such a scheme was possible. It appears that the technique is very similar to the standard migration scheme, with only additional weights in the imaging operator (Chauris and Cocher, 2018). These new operators are explicit, simple in terms of implementation and excellent preconditioners (a way to speed up the resolution of the inverse problem) for example for the full waveform inversion. They offer new perspectives for the stochastic imaging.
The thesis has two main objectives:
Better understand the limitations of the direct approach. For example, how does the new approach behave when the input data are not dense at the surface (typically only a few sparse shot gathers)? Is the approach always valid in complex media as the theory seems to indicate?
Extend the method beyond the acoustic approximation. The objective is to take into account the variable density, anisotropy and elastic properties of the model.
Applications include the imaging of the first meters until the first kilometers.
ProfileA strong background in maths or physics is important to understand and extend the approach. It is also essential to have had an experience in programming (e.g. C, Fortran, python ). The candidate should be motivated for investigating geophysical applications, in particular in the context of seismic
FundingAutre type de financement