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Laboratories of Image, Signal processing and Acoustics - Ecole polytechnique de Bruxelles / Faculté des Sciences

Adjoint-based geoacoustic inversion

The adjoint method of optimal control is a technique used for calculating an exact expression of the gradient of a cost function that depends implicitly of the control variables with respect to which one has to differentiate. The method avoids the time consuming calculation of the implicit function derivative, and is thus extremely well suited to optimal control problems. Adjoint-based optimization schemes are especially attractive when the use of a low-dimensional parameterization in combination with classical meta-heuristic approaches is not feasible.

The problem of geoacoustic inversion is posed as a boundary controllability problem by means of an analytic multi-frequency adjoint model derived from parabolic-type approximations. Recent extensions of the approach include adjoint-based geoacoustic inversion with an uncertain sound speed profile and the inversion of sediment dynamics in very shallow waters (rivers, estuaries and coasts).