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Communication Dans Un Congrès Année : 2024

The extended Dedicated Lithospheric field model (xDLFI) and its interpretation in terms of global magnetic crustal thickness

Résumé

Detailed mapping of the Earth's magnetic field brings key constraints on the composition, dynamics, and history of the crust. Satellite and near-surface measurements detect different length scales. We build a CHAMP and Swarm satellite dataset and combine it with the World Digital Magnetic Anomaly Map: version 2.1 (Dyment et al., IUGG Berlin, 2023), the most globally complete grid of airborne and marine scalar anomaly data. We then derive a lithospheric magnetic field model in Spherical Harmonics to degree 1500. Recovering such a high degree expansion requires estimating 2,253,000 parameters, which can hardly be achieved through a single global inversion. Therefore, we follow a regional approach that allows us to perform a series of independent regional linear inverse problems using robust parallel procedures, to deal regionally with the Backus effect in equatorial regions, and to assess independently each regional model. The series of regional model is then transformed into standard Spherical Harmonics by fast spherical transform. The general protocol is given in Thébault et al. "A Spherical Harmonic Model of Earth's Lithospheric Magnetic Field up to Degree 1050." Geophysical Research Letters 48.21 (2021): e2021GL095147) and was updated for this study to account for the most recent SWARM data and the updated WDMAM 2.1 near surface compilation. We then interpret the lithospheric magnetic field model in terms of magnetic crustal thickness for the large scales. Our strategy, which relies solely on magnetic field measurements and statistical properties of the crustal magnetic field, differs considerably from previous studies in which large spatial scales down to about 2500 km are constrained by global Moho depth models. Here, we process the SH lithospheric magnetic field model in both the spectral and the geographical domains without seismic a priori information. Preliminary results confirm that statistically the Moho depth is a magnetic boundary for the large magnetic spatial scales.
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hal-04545257 , version 1 (13-04-2024)

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Domaine public

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  • HAL Id : hal-04545257 , version 1

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Erwan Thébault, Gauthier Hulot. The extended Dedicated Lithospheric field model (xDLFI) and its interpretation in terms of global magnetic crustal thickness. Swarm 10 Year Anniversary & Science Conference, European Space Agency; Danish Technical University, Apr 2024, Copenhague, Denmark. ⟨hal-04545257⟩
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