In this collaborative project between CAU Kiel and GFZ in Potsdam, we aim to estimate the properties of the magnetic lithosphere on a global scale (magnetization, thickness, composition). The magnetic lithosphere, the part of crust and upper mantle that can contain magnetization, is studied by a combination of gravity and magnetic data from recent and ongoing satellite missions like GOCE, CHAMP and Swarm. The combined view allows for the first time a detailed sensitivity study of possible deep-seated magnetization in the lithosphere.
At CAU, the gravity gradients available from recent satellite missions are used to characterize the geometry and the density contrast at the transition from crust to upper mantle. Gravity gradients have a depth sensitivity, which makes them well suited for this analysis, and especially the use of the non-vertical tensor components is exploited to control the model geometry and to address the presence of lower crustal bodies. The model is based on available constraints.
At GFZ, we invert CHAMP and SWARM magnetic data in order to obtain a global model of the vertical integrated magnetization, without a-priori information. In the next step, we use information from existing magnetic crustal thickness models in the inversion of the satellite magnetic data. This information is introduced in the inversion thanks to a scheme of successive regional analyses by means of wavelets, and the outcome is a 3D magnetization model.
We combine the output of the magnetic and the gravity models in order to study the sensitivity of magnetic data in respect to realistic variations of the magnetization geometry. Different gravity derived models are used in order to constrain its geometry (lateral variation and thickness). The different resulting magnetization models are decomposed in their non-visible and visible parts, so that the signal of the latter can be meaningfully compared to the magnetic data. Finally, an inversion of magnetic data under the constraints provided by the gravity, seismic and thermal data is implemented.
Our aim is that the outcome of our study will contribute to the debate about the possibility of upper mantle magnetization and will allow us to discuss the petrological implications. These are related closely to the tectonic setting and dynamic evolution of the Earth system.
2016 - 2018