PBO station P150 on Martis Peak, California

Plate Boundary Observatory Site P150 on Martis Peak, California. Data from this site are available via UNAVCO. Photo by Vince Cronin.

Documents for the GETSI workshop at the Earth Educators' Rendezvous, 2018

Website for this GETSI module

GPS, Strain, and Earthquakes

NOTE that the most current module materials can be downloaded via the link provided above. Some of the files linked below were derived from this resource set on or about 5 July 2018.

UNAVCO is "a non-profit university-governed consortium [that] facilitates geoscience research and education using geodesy." The public resources of UNAVCO are available via, including data, software, and the many products of its education and outreach efforts. More information about UNAVCO is available at

Documents used or referenced during the workshop (in approximate order of use)

Introduction and motivation: (lowres pdf, 27.6 MB) [highres pdf, 175.4 MB] [JPEG images, 27.8 MB total] [Keynote original 158.4 MB]

Overview of module: (lowres pdf, 6.9 MB) [highres pdf, 10.1 MB] [JPEG images, 7 MB total] [Keynote original 9.7 MB]

GPS/GNSS Basics: (pdf, 34.4 MB) [PowerPoint original 32.2 MB]

GPS strain analysis (lowres pdf, 13.7 MB) [highres pdf, 33.7 MB] [JPEG images, 21 MB total] [Keynote original 40.9 MB]

Cascadia strain example: (pdf, 1.8 MB) [PowerPoint original 1.9 MB]

Graphic summary of the triangle-strain analysis: (pdf, 3.1 MB) [PowerPoint original 3.1 MB]

A relevant physical model

Your turn to do an analysis: (lowres pdf, 2.4 MB) [highres pdf, 5.3 MB] [JPEG images, 3.1 MB total] [Keynote original 5.9 MB]

Wasatch Example

How to find PBO GPS data:

Input data sources
GPS data for site P088:
GPS data for site P116:
GPS data for site COON:

Strain calculators
Excel calculator:
MatLab calculator:
Mathematica calculator:

How to interpret the strain calculator output:

USGS Quaternary Fault and Fold Database of the United States:

Additional documents related to this module used in Vince Cronin's Intro to Structural Geology course

Relevant UNAVCO/IRIS animations and videos

  1. UNAVCO videos on U-Tube:
  2. Animation-and-video homepage at UNAVCO:
  3. Earthscope's geodetic component -- Plate Boundary Observatory (PBO) overview:
  4. GPS Measures Deformation in Subduction Zones: Ocean/continent: or, for direct download,
  5. GPS Measures Deformation in Subduction Zone: Island Arc Setting: or, for direct download,
  6. GPS Records Variable Deformation across a Subduction Zone: or, for direct download,
  7. What can GPS tell us about future earthquakes? or, for a direct download,
  8. Sendai/Tohoku-oki earthquake displacements using 1 Hz data (by Ronni Grapenthin):
  9. GPS as an essential component of Cascadia earthquake early warning: or, for a direct download,
  10. ShakeAlert: Earthquake Early Warning System for Napa earthquake 2014: or, for direct download,
  11. Basin & Range: GPS measures extension: or, for direct download,
  12. Tectonics & Earthquakes of the Himalaya: or, for direct download,
  13. Volcano Monitoring: Measuring Deformation and Tilt with GPS: or, for direct download,
  14. Glaciers are retreating. How can we measure the full ice loss?
  15. Plate tectonics 540Ma to the modern world, from Chris Scotese:
  16. Plate tectonics 240Ma to 250 million years in the future, from Chris Scotese:


This GETSI module would not exist without the efforts of many people at UNAVCO and elsewhere. The UNAVCO Community provided the collaborative environment in which we could create resources to facilitate student learning about an important topic that was not represented in the undergraduate geoscience curriculum. The book Structural Geology Algorithms by Rick Allmendinger, Nestor Cardozo and Don Fisher (2012, Cambridge University Press) provided a clear explanation of relevant topics -- it served as an initial ramp at the base of the learning curve. Bill Hammond and Corné Kreemer of the University of Nevada-Reno have been unfailingly generous with their time, serving as our geodetic experts. Phil Resor (Wesleyan University) and I have broadly similar backgrounds as structural geologists, but Phil has brought a different level of intelligence, energy and creativity to the project. He is the author of the MatLab resources and (with input from Hammond) the lead author of the Napa Earthquake unit. Shelly Olds (UNAVCO) encouraged the initial development of these resources, and Beth Pratt-Sitaula (also UNAVCO) has been the driving force behind the reformulation of the first-gen resources into a coherent GETSI module. Donna Charlevoix and Meghan Miller have provided generous institutional support from UNAVCO. Nancy West helped us to keep the cognitive level of the resources developed for this module within the range of average undergraduate geoscience students.
— Vince Cronin

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