Using Earthscope Plate Boundary Observatory GPS velocities to introduce strain to undergraduate structural geology students Abstract


  • Strain and deformation are fundamental topics of undergraduate structural geology courses. Basic concepts are often introduced through images of beautiful, but rarely encountered, deformed fossils. We have developed an alternative module that builds students’ intuition for concepts of deformation including translation, rotation, and strain through physical model manipulation followed by qualitative and quantitative exploration of EarthScope Plate Boundary Observatory (PBO) data.
    Students determine the instantaneous deformation rate of a triangle on the earth’s surface defined by three PBO GPS sites. With six known quantities (north and east velocities for each point), and six unknowns (north and east translation, rotation, and three independent strain components) the problem is perfectly constrained. Students start by manipulating physical models to build intuition regarding homogeneous strain. After this experimentation, they complete an exercise applying their newly developed intuition to GPS velocity fields. The final assignment requires students to compute site velocities and uncertainties from PBO data and use these results to calculate translation, rotation, and strain rate. Supporting materials include: 1) a strain primer, 2) a strain calculator, 3) vector and matrix algebra background material, and 4) an extension for capable students to develop their own code.
    By exploring GPS triplets from a variety of tectonic environments (examples provided) students not only learn concepts of strain, but also make connections between strain and geologic structures. Examples from active tectonic areas also provide clear societal relevance to the study of crustal deformation. Finally, with more than 1200 PBO stations to choose from, the possibilities for student exploration are extensive. The module will be tested this fall in courses taught by the authors and will ultimately be accessible from the Science Education Resource Center (SERC), UNAVCO and EarthScope websites.

publication date

  • 2012

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