Sommer, Malte (2017) The application of Krylov subspace methods for the calculation of forward solutions and model sensitivities of 3D time domain marine controlled source electromagnetic problems. (PhD/ Doctoral thesis), Christian-Albrechts-Universität Kiel, Kiel, Germany, 82 pp.

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Abstract

To reduce the run-times of 3D modeling and inversion software for the interpretation of marine controlled source electromagnetics (CSEM) in time domain, the implementation of efficient algorithms on massive parallel hardware is presented. Two forward modeling implementations as well as an implementation for sensitivity calculation are illustrated. The first forward code is an implementation of the spectral Lanczos decomposition method on a graphics processing unit (GPU). The applicability of the code for a CSEM system, how it is used at GEOMAR, is demonstrated. In the second forward code, the SLDM is replaced by the more efficient Rational Krylov Subspace Method (RKSM). This reduces the dimension and run-time of the problem drastically. The accuracy of the code is investigated for different models and conductivity contrasts. The run-times of SLDM and RKSM are compared on different architectures. The sensitivities are computed with the MOR-method (Model Order Reduction). It is shown that the method works and the applicability to a real data set is shown.

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