G&M3D 1.0: an Interactive Framework for 3D Model Construction and Forward Calculation of Potential Fields

Abstract. Building source models and performing forward calculations are fundamental for processing, analyzing, and interpreting geophysical data. However, there are rare open-source tools available that allow for both the flexible and interactive construction of source models and potential-field forward calculations. To address this gap, we developed a new Qt-based software called G&M3D 1.0, which supports interactive 3D model construction and provides accurate and efficient forward modelling. G&M3D 1.0 features two core functionalities: (1) constructing 3D gravity and magnetic source models and (2) calculating and visualizing their gravity/magnetic fields, as well as their gradient fields. In the 3D Modelling Module, rectangular prisms are used to approximate anomalous geological bodies, striking a balance between computational efficiency and geometric flexibility. Users can conveniently create 3D models with regular shapes, like spheres, cuboids, cylinders, and prismoids, each having variable densities or magnetic parameters. Complex structures can be modelled using the Irregular (Layer-Building) tool, which is especially suitable for stratigraphic or faulted formations. In addition, the Forward-Modelling Module allows for the rapid calculation, visualization, and saving of gravity anomalies, gravity gradients, total magnetic intensity, and magnetic gradients generated by the created 3D sources. To improve the efficiency of the gravity and magnetic forward calculations, the software employs a 2D discrete convolution algorithm. G&M3D 1.0 offers several significant advantages, including open-source accessibility, flexible interactive operations, an intuitive 3D modelling interface, efficient forward computation, and excellent file portability. As a demonstration of its capabilities, we utilized G&M3D 1.0 for forward gravity modelling over a salt dome at Vinton Dome in southern Louisiana, U.S., providing validation of its accuracy and practicality.