Joint inversion of marine magnetotelluric and gravity data incorporating seismic constraints: Preliminary results of sub-basalt imaging off the Faroe Shelf

International audience Breakup of the North Atlantic during the early tertiary was accompanied by widespread and massive magmatism, resulting in the coverage of large areas of the North Atlantic with flood basalts. These flood basalts hamper seismic investigations of underlying sequences and thus th...

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Bibliographic Details
Published in:Earth and Planetary Science Letters
Main Authors: Jegen, Marion, Hobbs, Richard, Tarits, Pascal, Chave, Alan D.
Other Authors: Leibniz-Institut für Meereswissenschaften (IFM-GEOMAR), Department of Earth Science, Durham University, Domaines Océaniques (LDO), Centre National de la Recherche Scientifique (CNRS)-Institut d'écologie et environnement-Observatoire des Sciences de l'Univers-Université de Brest (UBO)-Institut national des sciences de l'Univers (INSU - CNRS), Université européenne de Bretagne - European University of Brittany (UEB)
Format: Article in Journal/Newspaper
Language:English
Published: HAL CCSD 2009
Subjects:
Online Access:https://hal-insu.archives-ouvertes.fr/insu-00422104
https://doi.org/10.1016/j.epsl.2009.02.018
Description
Summary:International audience Breakup of the North Atlantic during the early tertiary was accompanied by widespread and massive magmatism, resulting in the coverage of large areas of the North Atlantic with flood basalts. These flood basalts hamper seismic investigations of underlying sequences and thus the understanding of the rifting, subsidence and evolution of the margin which, in turn, increases the risk for hydrocarbon exploration. In this paper we present a methodology for the simultaneous joint inversion of diverse geophysical datasets, i.e. free air gravity and magnetotelluric soundings (MT) using seismic a priori constraints. The attraction of the joint inversion approach is that different geophysical measurements are sensitive to different properties of the sub-surface, so through joint inversion we significantly reduce the null space and produce a single model that fits all datasets within a predefined tolerance. Using sensitivity analysis of synthetic data, we show how each data set contains complementary important information of the supra and sub-basalt structure. While separate inversions of individual datasets fail to image through the basalt layer, our joint inversion approach leads to a much improved sub-basalt structure. Application of the joint inversion algorithm to satellite gravity data and MT data acquired on the FLARE10 seismic line south west of Faroe islands supports the existence of a 1 km to 2 km thick low velocity region that might be indicative of the existence of a sedimentary basin underneath the basalt layer. Though in this paper we demonstrate the use of joint inversion on a sub-basalt target, we believe it has wider applicability to other areas where conventional seismic imaging fails.