UBC-GIF or VP Suite inversion?

Geoscience ANALYST Pro Geophysics allows you to use both UBC-GIF and VP Geophysics Suite inversion programs. But the question is: when should I use which?

“UBC-GIF and VP Suite programs are complementary, and the combination gives one the ultimate flexibility in potential-field inversion,” says Kristofer Davis, Scientific Programmer at Mira Geoscience. “Both UBC-GIF and VP programs can run heterogeneous inversion of potential fields and electromagnetic data. With UBC-GIF, you can do fast, reliable, physical property inversions whereas VP offers geological-model parameterization with direct inversion for 3D geological contact geometry in addition to conventional grid parameterization.” A cross-sectional comparison of inversion options (property versus geometry) is provided below.

The UBC-GIF Suite is comprised of geophysical forward modelling and inversion programs designed to be fast, simple, and easy to use. The published methodologies of UBC-GIF have shown consistent and reproducible results for over 25 years. These programs are parallelized and utilize the wavelet transformation making them ideal for large-scale exploration in green-field scenarios. With the proper tools, one can take advantage of these programs by incorporating constraints based on observed geology directly into the inversions. Simple ASCII-based formatting of the input and output files makes the results straightforward to share and archive.

Cross-section of GRAV3D inversion of the Boulia, Queenland, regional gravity data set. The inversion reproduces the observed data to 2 mGal. Density contrasts range from –0.05 to 0.05 g/cc. The model slice is approximately 16 km by 160 km. There is a 2x vertical exaggeration.

The VP Geophysics Suite products differ in their approach to geophysical inversion by using a model that is defined by rock type, discretized to the centimetre vertically. This unique setup, in concert with four different inversion styles, gives the geoscientist full control to test hypotheses, extend geology, or discover new prospective areas. The geometry-based inversion recovers interfaces at depth and is best utilized by inverting for geological contacts under cover, modelling depth of basement, or intrusive geometry. Homogeneous inversion can solve for bulk properties such as density, magnetic susceptibility (and remanence), or electrical conductivity per geological domain. In addition, practical features such as the ability to incise a local model of interest into a regional model and optimizing the DC shift of the predicted data can minimize data pre-processing.

Cross-section of VPmg geometry inversion of the Boulia, Queensland, regional gravity data set to solve for the interface to the basement. The initial model was a two-layer model with a horizontal basement contact. The basement was assumed to be 2.75 g/cc with a cover of 2.40 g/cc. The inversion reproduces the observed data to 2 mGal. The model slice is approximately 16 km by 160 km. There is a 2x vertical exaggeration.

Kristofer Davis – Scientific Programmer

Kristofer completed his PhD in Geophysics at the Colorado School of Mines. As a Post-Doctoral Researcher at UBC he worked on several advanced problems in geophysical inversion, focusing, amongst other research areas, on development of software workflows to support constrained geophysical inversion. His industry and academic background provide the ideal experience to continue development of our VP Geophysics Suite products, Geoscience ANALYST Pro Geophysics, and our other geophysical tools and workflows. Kristofer is based in Vancouver.