Photogrammetric techniques for analyzing displacement, strain, and structural geometry in physical models: Application to the growth of monoclinal basement uplifts.

Physical models have been widely used to study geological structures for more than one hundred years. The greatest benefit of physical models is that with proper scaling of model dimensions and materials, researchers can directly observe structural or tectonic processes that take millions of years to occur naturally. Despite this benefit, however, use of physical models is not widespread because their construction and analysis is commonly labor-intensive work that yields largely qualitative information on structural geometry and limited quantitative information on displacement and strain. This paper describes how close-range photogrammetry can be used to obtain quantitative information on the geometry, displacement, and strain patterns in an evolving physical model. The technique is an inexpensive, high-resolution, noninvasive, and efficient method that uses standard commercial software and a digital camera to determine the x, y, z positions of high-contrast markers placed on the model surface. The model geometry at any given time is defined by the positions of all the markers, whereas strain and displacement are obtained by comparing, or tracking, the positions of the markers at different times during an experiment. We present as an example application of the technique, an analysis of scaled physical models of monoclimes that form above basement-involved reverse faults with differing displacement distributions. Using close-range photogrammetry, we are able to link fault displacement and lateral propagation history to unique, evolving, three-dimensional (3-D) geometries and deformation patterns that are unlikely to be revealed by other analysis techniques. [ABSTRACT FROM AUTHOR]