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, open-source tools that allow for both the flexible and interactive construction of source models and potential-field forward calculations are rare. To address this gap, we develop a new Qt-based software called G&M3D 1.0 (Gravity and Magnetic 3D modelling), which supports interactive three-dimensional (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, user-defined anomalous bodies are internally discretized into assemblies of rectangular prisms for forward calculation. Based on this prism-based representation, users can conveniently construct regular bodies, such as spheres, cuboids, cylinders, ellipsoids and prismoids, and assign density contrast or magnetic parameters to them. Complex structures can be represented 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 enhance computational efficiency, the software employs a 2D discrete convolution algorithm for the gravity and magnetic forward calculations. 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 use G&M3D 1.0 for forward gravity modelling over a salt dome at Vinton Dome in southern Louisiana, U.S., validating its accuracy and practicality.