Integrated Three-Dimensional Gravity Modelling in Different Types of Geological Environments

Three-dimensional (3-D) interactive modelling permits an integrated processing and interpretation of geoid, gravity and magnetic fields, yielding an improved geologic interpretation. Generally 3-D models are constructed by triangulated polyhedra to which constant density and/or induced and remnant susceptibility are assigned. Interactive modifications of model parameters (geometry, density, susceptibility), access to the numerical modelling process, and direct visualization of both calculated and measured fields of gravity and magnetics, enable the interpreter to design the model as realistic as possible (forward modelling). An approach is described to integrate constraining data into the interactive modelling process by means of visualizing and combining geodata with the density/susceptibility model. This visual combination of different 2- and 3-D models enables a quantitative comparison and adjustment, and results in a model comprising as much independently derived information as possible. The definition of 'geo-objects', which link geoscientific vocabulary with geometrical elements of the model, provides a comfort environment for interpretational discussions in front of the computer monitor. We present different cases of three dimensional density modelling using an object oriented GIS module (IGMAS); from 1) Subduction zone (Andes), 2) Collision zone (Alps), 3) Transform zone (Dead Sea Rift and Aqaba), 4) Sedimentary basins (North west Germany), and 5) Continental Rift systems (East African Rift). The modelling helped to shed some light on variations of subduction geometries and crustal thickness along the Andes, on the collision and interaction of the European and Adriatic plates, basin structures and sedimentary thickness in Germany and underlying rift structures in the Afro-Arabian rift system. The results demonstrate the capability and robustness of three-dimensional potential field modelling to study major geological processes that constantly change our planet.