Forward Modeling of the Fennoscandian Lithospheric Field Using Spherical Prisms

Abstract:

We show the first results of a sensitivity analysis used to determine if and how induced and remanent magnetization can be distinguished in magnetic data from the Swarm satellite mission. The Swarm satellite magnetic data have higher resolution (to 200km wavelength) and accuracy than previous satellite missions, which makes them complimentary to airborne magnetic surveys.

However, calculations at satellite level require a spherical modeling approach. We present newly developed software for magnetic field modeling that allows a fast calculation of the crustal magnetic field. The crustal model is represented as a set of spherical prisms, tesseroids. In our setup, we can model both the direction and amplitude of the inducing field and its temporal variations. Synthetic models, global and local tests using the geometry of CRUST1.0, show that our modeling approach leads to similar results as previous applied modeling techniques (global or local), but have a higher precision.

This approach is applied to the area of the Fennoscandian shield and the NE Atlantic. For the Fennoscandian shield remanent magnetization has been proposed as strong source for the magnetic anomalies on a regional scale. We want to validate the effect of induced and remanent magnetization in magnetic data at the height of satellites and airborne surveys. An important outcome of this combined view is a better understanding of the deepest magnetic sources in the lithosphere and the related thermal boundaries (e.g. Curie temperature). As the first example of this approach, we are going to show an initial model based on petrophysical maps of the region (susceptibility and total magnetization) and how the susceptibility distribution in deep crustal layers may affect the observed field.