Phil Resor • Vince Cronin • Beth Pratt-Sitaula

1. Using Earthscope Plate Boundary Observatory GPS velocities to introduce strain to undergraduate structural geology students Phil Resor • Vince Cronin • Beth Pratt-Sitaula Bill Hammond • Corné Kreemer • Shelley Olds • Nancy West

2. Strain is a fundamental concept introduced in structural geology class http://marlimillerphoto.com/SrD-53.html • We have developed an alternative module using examples from GPS geodesy Typically introduced through images of beautiful [but rare] deformed fossils

3. GPS Strain Module Developed by technical team with UNAVCO support Faculty Developers Vince C (Baylor) Phil R (Wesleyan) Geodesy Experts Bill H & Corne K. (UNReno) Education Specialists Beth P & Nancy W (UNAVCO) • Development workshop at UNReno in June 2012 • Ongoing collaboration through 2012-2013 academic year

4. GPS geodesy can be used to effectively introduce strain concepts • Strain fundamentals introduced through analysis of GPS velocity fields • Students develop their intuition incrementally • Preliminary assessment suggests that the module is effective

5. Plate Boundary Observatory is a rich data set for exploring strain • Spans western North America plate boundary • Managed by UNAVCO: non-profit consortium NSF EarthScope’s 1100 station GPS network

6. Deformation explored through the problem of a constant strain triangle • North and east velocities for each station provide 6 known quantities • Solve for 6 unknown quantities: north and east translation, rotation, 3 strain components Triangle is defined by 3 GPS stations Davis et al, 2012

7. Students are first introduced to GPS and GPS time series • How to locate and download data Add Cascadia example time series? • How to assess time-series data quality GPS basics

8. Students begin their exploration with a simple physical model • Circle provides strain marker • Students act as “GPS stations” Model made from widely available material (sport shirt)

9. Students apply their conceptual understanding to GPS velocity fields • Students sketch out deformed state and describe deformation Add Cascadia example figure? • Students qualitatively analyze example with real GPS velocities Sketches illustrate various end-member deformations

10. Students complete the assignment by computing strain from GPS velocities • Homework solving for common set of stations Add Cascadia example figure? • Final project analyzing self-selected GPS triangles Introduction to quantitative analysis including worked example

11. Resources are available for student and faculty support • Vector and matrix algebra background material: supplemental “refresher” • Strain calculator (implemented in Excel, MATLAB, Mathematica) Strain primer: Introduces required background on infinitesimal/instantaneous strain

12. Efficacy assessed through pre- and post-tests on fundamental concepts Results

13. Preliminary Outcomes Students are able to: Describe meaning of GPS vectors Describe strain qualitativelybased on velocity vectors Back-envelope calculationsof strain rate (ex. across WA) mini lectures, groupactivities (physical models, small exercises), readings,homework

14. Primary Outcomes Students will be able to: • Access & download Plate Boundary Observatory (PBO) data for 3-station triangles • Do calculations to determine how triangle has rotated, translated, distorted • Analyze geological implications of strain and compare to: • Local structures • Regional earthquake hazard • Focal mechanisms (optional)

15. For Discussion Questions Suggestions/requests Interested beta-testers (winter-spring 2013)?