Guidelines and Strategies for Model Building and Interpretation in 3D Space
Roddy Muir, Alan Gibbs, Colin Dunlop, J. Ryan Shackleton, and Gareth Johnson
Midland Valley Exploration, Ltd., Glasgow, Scotland, UK
Geologists routinely work with a wide range of geological and geophysical data in their attempts to build realistic 3D models of the sub-surface. The approach that the geologist takes to interpretation and model building can vary considerably depending on their background and training, and the techniques and technology that they have access to, chosen to adopt or have been advised to use.
The traditional learning approach that is still taught in most universities and colleges is to start on paper in 2D by learning how to produce field maps and cross-sections. The map will illustrate the outcrop pattern (distribution of rock types/units) at the surface and the section will show how these rock units and associated structures extend beneath the surface. The intersection of the surface geology with topography can be used to help project surfaces and structures at depth and combined with various geometric construction and stereographic projection techniques it is possible to build a robust 3D model of the sub-surface geology. Working on paper, it often helps to visualise the 3D aspects of the geology in the form of a "fence diagram" or a "block diagram", but this relies on the geologist having some artistic/technical skill. It requires considerable knowledge and practice to be able to sketch a block diagram on paper in the correct orientation(s) to best demonstrate the 3D aspects of the geology and structural relationships in your area of interest.
The advent of 3D model building and validation software has dramatically improved our ability to construct and visualise the often complex geology of our planet (and other planets). It is now possible to collect data, generate maps and cross-sections, build and test 3D models and visualise all of this entirely in a digital environment. The same geological skills that were traditionally taught on paper can now be easily demonstrated on tablet devices in the field, and the quality of a 3D model now depends on the knowledge and thinking skills of the geologist rather than their artistic ability.
AAPG Search and Discovery Article #120140© 2014 AAPG Hedberg Conference 3D Structural Geologic Interpretation: Earth, Mind and Machine, June 23-27, 2013, Reno, Nevada