Methodology:

Crustal density and susceptibility distribution is inferred from "Variation of Information" joint inversion of airborne gravity and magnetic data. The inversion is carried out with the academic software JIF3D (https://sourceforge.net/projects/jif3d/) developed by Max Moorkamp.

The density and susceptibility inversion model are discretised into meshes with equal horizontal cell sizes of 250m. The vertical cell size is 100m at the surface. The vertical cell size increases with depth by a factor 1.1 for each cell. Increasing vertical cell size with depth is introduced to account for decreasing resolution with increasing distance to the source in potential field applications.

Additionally, a padding area of 20% around the study area is added to avoid edge effects. The resulting inversion mesh contains 130 cells east-west direction, 314 cells in north-south direction and 33 cells in the z direction (20 km below sea level). To constrain the model geometry, the bedrock topography and Moho depths are used as model boundaries.

All cells are set to a starting value of 0 kg m-3 and 0 SI for density and susceptibility, respectively. The density and susceptibility values are iteratively updated during the joint inversion process.

Python code for preparing input data, setting up the inversion and plotting the results is openly accessible through zenodo.org (https://doi.org/10.5281/zenodo.14016296).

Data collection:

The data preparation and the inversion set up is performed in python (version 3.10.11). The inversion itself is carried out in the JIF3D software using a Linux terminal.

Data quality:

The mean residual between observed and inverted gravity and magnetic field is 0.1 mGal and -0.2 nT, with a standard deviation of 2.5 mGal and 3.5 nT.

The data have a horizontal resolution of 250 m and a vertical resolution of 100 m, which increases with a factor of 1.1 with depth.