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When estimating hydraulic transmissivity the question of parameterization is of great importance. The transmissivity is assumed to be a piecewise constant space dependent function and the unknowns are both the transmissivity values and the zonation, the partition of the domain whose parts correspond to the zones where the transmissivity is constant.… (More)

- Guy Chavent
- 1998

In order to deene an optimal true amplitude prestack depth migration for mul-tishot and multitrace data, we develop a general methodology based on the least squares data misst function associated with a forward model. The amplitude of the migrated events are restored at best for any given geometry and any given preliminary ltering and amplitude correction… (More)

- G. Chavent, K. Kunischy
- 1996

1 Problem statement and functions of bounded variation We consider the problem of nding approximate solutions to Tu = z (1.1) where T is a bounded linear operator from L 2 (() to a Hilbert space Y by using regularization techniques based on bounded variation functionals. Here is a bounded domain in IR n with Lipschitzian boundary and z 2 Y. The operator T… (More)

- Guy Chavent, Karl Kunisch
- SIAM Journal of Applied Mathematics
- 1996

A new method for formulating and solving parameter estimation problems based on Fenchel duality is presented. The partial diierential equation is considered as a contraint in a least squares type formulation and is realized as a penalty term involving the primal and dual energy functionals associated with the diierential equation. Splitting algorithms and… (More)

- Guy Chavent
- 1994

We show in this paper how the application of convex duality leads to various reformulations of the classical non optimizable least squares approach to waveform prestack inversion. These reformulations search all for i) a background velocity model and ii) a re-ectivity model deened in the time domain, and linked to the usual depth reeectivity model by… (More)

- René-Edouard Plessix, Yann-Hervé De Roeck, Guy Chavent
- SIAM J. Scientific Computing
- 1998

- Guy Chavent, Karl Kunisch, Karl Franzens
- 1999

We consider the problem of determining the diffusion coefficient a(x) in a 2D elliptic equation from a distributed measurement z in H1 of the solution u of the equation. For a problem with a simple geometry, we give conditions under which the first derivative of the b = 1=a 7 ! u mapping is coercive. Then we show that its non linearity in a direction d… (More)

- Guy Chavent
- ArXiv
- 2009

We introduce a new global pressure formulation for immiscible three-phase compressible flows in porous media which is fully equivalent to the original equations, unlike the one introduced in [5]. In this formulation, the total volumetric flow of the three fluids and the global pressure follow a classical Darcy law, which simplifies the resolution of the… (More)

- Raphaël di Chiara Roupert, Guy Chavent, Gerhard Schäfer
- J. Comput. Physics
- 2010