Universität zu Köln

Seidel, Marc ORCID: 0000-0002-6579-6463 (2019). A 3D Time Domain CSEM Forward Modeling Code using custEM and FEniCS. PhD thesis, Universität zu Köln.

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Abstract

A new 3D time domain CSEM forward modeling code TDcustEM built upon the recently published open-source frequency domain code custEM and the open-source finite element toolbox FEniCS is presented. The transformation of the frequency domain data provided by custEM is performed by a Fast Hankel Transform using 80 digital filter coefficients. 3D edge-based tetrahedral meshes generated by TetGen facilitate the calculation of syn- thetic data using topography, arbitrary source geometries and complex subsurface structures. To ensure precision and reliability of the new algorithm, calculated results of different CSEM setups and electromagnetic field components are cross-validated against analytic solutions as well as 1D and 3D time domain modeling codes. Certain modeling studies are conducted regarding possible interpolation and extrapola- tion techniques to reduce the number of necessary frequencies and therefore the compu- tational runtime, which is still an issue of convolutional time domain CSEM approaches. Additional modeling studies showed the importance of precise receiver positioning for measuring the horizontal components of the time derivative of the magnetic field. As the present thesis is embedded in the Collaborative Research Centre 806 – Our Way to Europe, three sedimentary deposits in the East African Rift Valley were subject to mul- tidimensional TEM surveys in the framework of this project. Common 1D (EMUPLUS) as well as laterally and spatially constrained (AarhusInv) in- version techniques were applied to the TEM field data. Sediment thicknesses as well as stratigraphic sequences of the investigated sedimentary basins were derived. An extensive 3D modeling study of one of the target areas representing a volcanically-formed basin including topography was performed using the newly developed TDcustEM code.

Item Type:	Thesis (PhD thesis)
Translated title:	Title Language UNSPECIFIED German
Creators:	Creators Email ORCID ORCID Put Code Seidel, Marc seidel@geo.uni-koeln.de orcid.org/0000-0002-6579-6463 UNSPECIFIED
URN:	urn:nbn:de:hbz:38-104898
Date:	2019
Language:	English
Faculty:	Faculty of Mathematics and Natural Sciences
Divisions:	Faculty of Mathematics and Natural Sciences > Department of Geosciences > Institute for Geophysics and Meteorology
Subjects:	Natural sciences and mathematics Earth sciences
Uncontrolled Keywords:	Keywords Language Applied Geophysics UNSPECIFIED 3D CSEM Modeling UNSPECIFIED Time domain UNSPECIFIED Finite Elements UNSPECIFIED custEM UNSPECIFIED FEniCS UNSPECIFIED
Date of oral exam:	25 November 2019
Referee:	Name Academic Title Tezkan, Bülent Prof. Dr. Hördt, Andreas Prof. Dr.
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/10489