Project description
Nonlinear inversion of full waveform cross-correlation
Waves carry information of media through which they propagate and provide non-invasive means to probe the unknown interior structure. Ambient noise imaging employs cross-correlations of seismic noise, from which seismic data are extracted for inversion. Current results are limited to exploiting only partial information such as travel-times, and perform qualitative or linearised inversions. The ERC-funded INCORWAVE project aims at developing a framework for quantitative nonlinear inversion of full-waveform cross-correlation in the frequency domain, with a focus on reconstructing viscoelastic parameters in Earth's subsurfaces and 3D solar flows. To deal with the high computational costs, cross-talk between parameters, ill-posedness and lack-of convexity of the inverse problem, the project employs efficient parametrisation and hierarchical model parameter inversion for high-resolution reconstructions.
Objective
Waves propagating through a complex medium provide a non-invasive way to probe its interior structures. In ambient noise imaging, the input data are the cross-correlation of the stochastic wavefields. To reconstruct the properties of the medium, the waveform inversion is formulated as an optimization problem involving a misfit function whose convexity plays a critical role in the achievable spatial resolution of the inversion results, especially in the absence of a priori information about the medium. Current inversions are often limited by computational cost, cross-talk between the physical quantities, and the use of single-scattering approximations. Project INCORWAVE proposes to create a new mathematical and computational framework for nonlinear inversion of full waveform cross-correlation. Two specific problems are considered: first, for the reconstruction of geophysical visco-elasticity tensors with applications to Earth's subsurface monitoring; secondly, for the reconstruction of three-dimensional flows in the Sun to characterize the poorly understood properties of deep solar convection. To improve the convexity of misfit functions, the inversion procedure of project INCORWAVE will follow a hierarchical progression which is established by selecting subsets of input data, unknown parameters, and frequencies. The choice of each of these subsets, as well as the associated misfit function, is controlled by criteria in form of convergence estimates. Indispensable to meaningful inversion is accurate modeling operators that describe the physics under consideration and that are adapted to the treatment of real data. For the reconstruction of the elasticity tensor, the project will develop a solver in terms of P- and S-potentials for heterogeneous media. A 3D global Sun vector-wave solver is created for the inversion of the convection component of the solar flow that does not bear symmetry.
Keywords
Programme(s)
- HORIZON.1.1 - European Research Council (ERC) Main Programme
Topic(s)
Funding Scheme
HORIZON-ERC - HORIZON ERC GrantsHost institution
78153 Le Chesnay Cedex
France