DGG 2021: Interdisciplinary 3D potential field modelling of complex lithospheric structures by IGMAS+

Abstract

We introduce an approach for 3D joint interpretation of potential fields and its derivatives under the condition of constraining data and information. The interactive 3D gravity and magnetic application IGMAS (Interactive Gravity and Magnetic Application System) has been around for more than 30 years, initially developed on a mainframe and then transferred to the first DOS PCs, before it was adapted to Linux in the ’90s and finally implemented as a cross-platform Java application with GUI called IGMAS+. The software has proven to be very fast, accurate and the GUI has been adapted for usability, once a model is established. Since 2019 IGMAS+ is maintained and developed in the Helmholtz Centre Potsdam – GFZ German Research Centre by the staff of Section 4.5 – Basin Modelling and ID2 – eScience Centre.

The core of IGMAS+ applies an analytical solution of the volume integral for the gravity and magnetic effect of a homogeneous body. It is based on the reduction of the three-folded integral to an integral over the bounding polyhedrons that are formed by triangles. Later the algorithm has been extended to cover all elements of the gravity tensor as well and the optimized storage enables fast least-squares inversion of densities and changes to the model geometry and this flexibility makes geometry changes easy. Because of the triangular model structure of model interfaces, IGMAS can handle complex, structures (multi-Z surfaces) like the overhangs of salt domes and variable densities due to voxelization.

To account for the curvature of the Earth, we use spherical geometries. This is particularly important for geophysical investigations at global scales. Therefore IGMAS+ is capable to handle models from big-scale to regional and small-scale models (meters) used in Applied Geophysics.

The model technique is user-friendly because it is highly interactive and operates in real-time by means of hardware-accelerated parallel calculations. Modelling is constrained by seismic and structural input from independent data sources and is essential toward a true integration of 3D thermal modelling.

We demonstrate the flexibility of the software by modelling structures of the South American and European lithosphere.