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# Zeitschrift für Analysis und ihre Anwendungen

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**Volume 12, Issue 2, 1993, pp. 327–341**

**DOI: 10.4171/ZAA/562**

Published online: 1993-06-30

Identifiability of the Transmissivity Coefficient in an Elliptic Boundary Value Problem

Gennadi Vainikko^{[1]}and Karl Kunisch

^{[2]}(1) Tartu University, Estonia

(2) Karl-Franzens-Universität Graz, Austria

We deal with a coefficient inverse problem describing the filtration of ground water in a region $\Omega \subset R^n, n ≥ 2$. Introducing a weak formulation of the problem, discretization and regularization methods can be constructed in a natural way. These methods converge to the normal solution of the problem, i.e. to a transmissivity coefficient of a minimal $L^2 (\Omega)$-norm. Thus a question about $L^2$-identifiability (identifiability among functions of the class $L^2 (\Omega)$ of the transmissivity coefficient arises. Our purpose is to describe subregions of $\Omega$ where the transmissivity coefficient is really $L^2$-identifiable or even $L^1$-identifiable. Thereby we succeed introducing physically realistic conditions on the data of the problem, e.g. piecewise smooth surfaces in $\Omega$ are allowed where the data of the inverse problem may have discontinuities. With some natural changes, our results about the $L^1$-identifiability extend known results about the identifiability among more smooth functions given by G. R. Richter [4], C. Chicone and J. Gerlach [1], and K. Kunisch [3].

*Keywords: *Inverse problems, ground water filtration problems, identifiability

Vainikko Gennadi, Kunisch Karl: Identifiability of the Transmissivity Coefficient in an Elliptic Boundary Value Problem. *Z. Anal. Anwend.* 12 (1993), 327-341. doi: 10.4171/ZAA/562