### Analysis of Domain Decomposition and Global Solvers for Controlled-Source Electromagnetics

#### Abstract

Electromagnetic signals have been used in Geophysics as a powerful tool to obtain information of the subsurface since many years ago. Controlled-source electromagnetic methods (CSEM) have shown to be a very valuable tool in off-shore hydrocarbon prospecting but also have been used in CO2 deposition monitoring and studies of the behaviour of coastal aquifers. In order to model the behaviour of electromagnetic ﬁelds in the subsurface, Maxwell’s equations -in our case two-dimensional- must be solved. The discretization of the equations is carried out by means of the ﬁnite element method, which in general leads to the resolution of large sparse linear systems that require robust computational algorithms. The aim of this presentation is to compare the efﬁciency of two different resolution strategies, in terms of CPU time, memory usage, among other criteria, namely: (a) Domain decomposition (DD): The domain where the equations are being solved is divided into a large number of small subdomains, leading to the iterative resolution of a large number of small linear systems. The algoritmhs that arise from this technique are meant to be implemented, for instance by using the standard MPI, in parallel architecture computers. (b) Global resolution: Unlike DD, the domain is not subdivided, which leads to a single large sparse linear system. In order to ﬁnd its solution we use the solver PARDISO, designed to run on shared-memory architecture computers.

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Güemes 3450

S3000GLN Santa Fe, Argentina

Phone: 54-342-4511594 / 4511595 Int. 1006

Fax: 54-342-4511169

E-mail: amca(at)santafe-conicet.gov.ar

**Asociación Argentina de Mecánica Computacional**Güemes 3450

S3000GLN Santa Fe, Argentina

Phone: 54-342-4511594 / 4511595 Int. 1006

Fax: 54-342-4511169

E-mail: amca(at)santafe-conicet.gov.ar

**ISSN 2591-3522**