Project

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Accounting for 3-D time-dependent, anisotropic electrical conductivity effects in global satellite induction studies

English title Accounting for 3-D time-dependent, anisotropic electrical conductivity effects in global satellite induction studies
Applicant Kuvshinov Alexey
Number 121837
Funding scheme Project funding
Research institution Institut für Geophysik ETH Zürich
Institution of higher education ETH Zurich - ETHZ
Main discipline Geophysics
Start/End 01.12.2009 - 30.04.2014
Approved amount 175'364.00
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All Disciplines (2)

Discipline
Geophysics
Mathematics

Keywords (7)

3-D global induction; magnetic field; Electromagnetic induction; mantle conductivity; Australian magnetovariational data; response functions; 3-D EM modelling and inversion

Lay Summary (English)

Lead
Lay summary
The project pursues three main goals: 1) development of new methodological tool to interpret regional magnetovariational data in a three-dimensional (3-D) frame; 2) application of this methodology to Australian geomagnetic array data; 3) recovery, using these data and the new methodology, of the 3-D electrical conductivity distribution in the upper mantle beneath the Australian continent and linking of this distribution with the tectonic and geological setting of the region. It is planned to recover from the data the new electromagnetic (EM) transfer functions recently introduced. To invert the data a comprehensive 3-D inversion approach will be used. To interpret the results we plan to link the recovered 3-D conductivity model with the models of different physical parameters recovered in the region by other geophysical/geological methods. Milestones of the project are: (1) Data preprocessing; (2) Source determination; (3) Multi-variate time series analysis of the data; (4) Compilation of an Australia conductance map; (5) Adaption of existing global 3-D forward and inverse solutions to our regional data; (6) Practical 3-D inversion of the data; (7) Interpretation of the recovered 3-D conductivity distribution in the upper mantle beneath Australia. It is expected that the information about the degree of lateral non-uniformity of the upper mantle conductivity in this region will be obtained. The experience in application of the new methodology to real experimental data will be gained. Finally a 3-D interpretational tool that can be useful for interpretation of data from continental-scale, multi-disciplinary projects - such as the ongoing US project "EarthScope" and the forthcoming European project "EuroArray" - will be developed.
Direct link to Lay Summary Last update: 21.02.2013

Responsible applicant and co-applicants

Employees

Publications

Publication
Global 3-D EM inversion of Sq variations based on simultaneous source and conductivity determination: Concept validation and resolution studies
Koch Stephan, Kuvshinov Alexei V. (2013), Global 3-D EM inversion of Sq variations based on simultaneous source and conductivity determination: Concept validation and resolution studies, in Geophysical Journal International, 195(1), 98-116.

Scientific events

Active participation

Title Type of contribution Title of article or contribution Date Place Persons involved
IAGA Meeting Talk given at a conference 3-D EM inversion of ground based geomagnetic Sq data. Concept and first results using Australian 25.03.2013 Merida, Mexico Kuvshinov Alexey; Koch Stephan;
EMTF Poster 3-D EM inversion of ground based geomagnetic Sq data. Concept and first results using Australian AWAGS array data 25.03.2013 Kirchhundem, Germany Koch Stephan; Kuvshinov Alexey;
21st EM-Workshop Poster Global 3-D EM inversion of ground observatory geomagnetic Sq data based on simultaneous source and conductivity determination. A concept and its validation 25.07.2012 Darwin, Australia Kuvshinov Alexey; Koch Stephan;
EMTF-Kolloqium Poster Towards 3D EM inversion of ground based geomagnetic Sq variations. Source determination 26.09.2011 Neustadt/Weinstraße, Germany, Germany Kuvshinov Alexey; Koch Stephan;


Abstract

We describe a project which focuses on a global-scale diffusion problem, namely that of electromagnetic (EM) induction. Time-varying magnetic fields of magnetospheric and ionospheric origin create current flow in the Earth’s mantle, and the magnetic effect of both source and response can be measured on and above the Earth’s surface. These effects constrain the electrical conductivity of the mantle, and have bearing on the question of the dynamics of the mantle. Our particular goal is to make use of the dense measurement coverage of the Earth provided by satellite magnetometers, and this creates challenges. To accurately model such data, one must take into account the anisotropic conductivity of the ionosphere, and its temporal changes. For that reason we plan to develop a flexible time-domain based numerical code to simulate magnetic field diffusion in the mantle and ionosphere with a three-dimensional (3-D) conductivity distribution, possibly time-varying. The approach is based on a finite difference approach both in space and time. This will differ from existing time-domain induction codes in spherical coordinates which rely either on spectral methods (using spherical harmonics) or the Fourier transform of frequency-domain results. The aim is to elaborate a numerical solution that will be faster and more accurate than conventional codes, especially for highly-contrasting media. There is a crucial need to correct the new data sets generated by current satellites, as well as those forthcoming from ESA’s Swarm mission, for the effects of time-variable conductivity of the ionosphere. We expect to be able to quantify the ionospheric effect and correct for it in the first instance, leading to improved estimates of 3-D conductivity of the mantle and more accurate recovery of the various sources of the geomagnetic field (such as core and lithospheric fields). The code should ultimately be capable of providing a flexible platform for complete inversion studies of the mantle.
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