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This module is part of a growing collection of classroom-tested materials developed by GETSI. The materials engage students in understanding the earth system as it intertwines with key societal issues. The collection is freely available and ready to be adapted by undergraduate educators across a range of courses including: general education or majors courses in Earth-focused disciplines such as geoscience or environmental science, social science, engineering, and other sciences, as well as courses for interdisciplinary programs.
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For the Instructor

This material supports the GPS, Strain, and Earthquakes GETSI Module. If you would like your students to have access to this material, we suggest you either point them at the Student Version which omits the framing pages with information designed for faculty (and this box). Or you can download these pages in several formats that you can include in your course website or local Learning Managment System. Learn more about using, modifying, and sharing GETSI teaching materials.

Welcome Students!

Understanding how the Earth's crust deforms is crucial in a variety of geoscience disciplines, including structural geology, tectonics, and hazards assessment (earthquake, volcano, landslide). Over the last couple of decades, the installation of numerous high-precision Global Positioning System (GPS) stations has dramatically increased our ability to measure this deformation (strain). However, GPS data are still only rarely included in undergraduate courses, even for geoscience majors. In this 2–3 week module, you will analyze GPS velocity data from triangles of adjacent GPS stations to determine the local strain. You will learn about strain and deformation in a much more intuitive and ongoing way, and see how these cutting-edge findings tie to regional geology and earthquake hazards. By the end of the module you will be able to
  1. Access and analyze GPS data in order to calculate and interpret ongoing strain in the region between three neighboring GPS stations.
  2. Synthesize how calculated local strain is related to regional tectonics and earthquake hazard and risk, and propose mitigation strategies.

Your instructor may choose to use all the units or just select a subset based on time and course focus.


Unit 1: Earthquake!

We all know what earthquakes are in a general sense, but what are the effects on a society from these crustal movements? This first unit is designed to help you better understand the human toll of earthquakes and the ways in which geoscientists study earthquakes. You will use a case study of the Magnitude 9.1 2011 Tohoku, Japan, earthquake. It starts with a short homework "scavenger hunt" in which you need to find a compelling video and information about the earthquake. Then, in class you will share some of what you found and do a series of think-pair-share exercises to investigate both the societal and scientific data about the earthquake.

Unit 2: Mashing It Up: Physical Models of Deformation and Strain

It can be much easier to understand geologic concepts if you get a chance to use physical models of real processes. In this unit, you will get to play with everyday materials such as bungee cords, rubber bands, stretchy fabric, index cards, silly putty, and sand to gain a more intuitive understanding of strain and deformation. It will be much easier to learn about concepts such as vector velocities, positive and negative extension, simple and pure shear, and strain ellipses through these hands-on models. Your instructor may do these experiments all in one class period or spread them out over a series of class periods. Some instructors may also choose to have you brush up on a variety of math concepts that help in better understanding strain, deformation, and GPS movements.

Reading Physical modeling exercises: your instructor will tell you which of these to use Supporting math materials for the module as a whole: your instructor will tell you if you will be using any of these.

Unit 3: Getting Started with GPS Data

We all have GPS receivers in our phones and other devices, but few people realize the power of GPS to measure movements as small as 1 millimeter per year. As the crust of the Earth moves and deforms, earthquakes must inevitably occur. By measuring crustal motions with high-precision GPS, we can do a better job of pinpointing earthquake hazards and take steps to reduce risk to lives and property. This is cutting-edge technology and research, and very few undergraduates learn how how to use GPS data in this way.

This unit provides essential background information on how GPS (global positioning system) actually works. You will learn how to access GPS location and velocity data from the Plate Boundary Observatory (PBO) using the same interface used by scientists from around the world. You will calculate total horizontal motion graphically and mathematically and tie the observed motions to local strain conceptually.

Unit 4: GPS and Infinitesimal Strain Analysis

In this unit you take your understanding of strain from the conceptual to the analytical. You will work with GPS velocity data from three stations in the same region that form an acute triangle. By investigating how the ellipse inscribed within this triangle deforms, you will learn about strain, strain ellipses, GPS, and how to tie these to regional geology and ongoing hazards. This unit contains the primary infinitesimal strain analysis for the module. The exercise that you and your peers will work on investigates three different GPS station triangles in three different tectonic regimes: Cascadia in Washington State, the Wasatch fault in Utah, and the San Andreas Fault in California. You will also read about earthquake scenarios for each region and tie the societal with the geologic.

Exercise files

GPS Strain Calculators: your instructor will tell you which of these to use.

Earthquake scenario document


Unit 5: 2014 South Napa Earthquake and GPS Strain

The 2014 South Napa earthquake was the first large earthquake (Magnitude 6) to occur within the Plate Boundary Observatory GPS network since installation. It provides an excellent example for studying crustal strain associated with the earthquake cycle of a strike-slip fault with clear societal relevance. The largest earthquake in the California Bay Area in twenty-five years, the South Napa earthquake caused hundreds of injuries and over $400 million in damages. This activity uses a single triangle of GPS stations, located to the west of the earthquake epicenter, to estimate both the interseismic strain rate ( movement between earthquakes) and coseismic displacement (motion during the earthquake).

Reading

Exercise files

GPS Strain Calculators: your instructor will tell you which of these to use.


Unit 6: Applying Strain and Earthquake Hazard Analyses to Different Regions

This final unit in the module gives you the chance to do your own small research project in an area of interest to you. You will select your own set of three GPS stations in your interest area, conduct a strain analysis of the region between the stations, and tie the findings to regional tectonics and societal impacts in a 5–7 minute class presentation. Your instructor will give you more exact instructions regarding his or her presentation expectations.

Final project assignment

  • Unit 6 "GPS, Strain, and Earthquakes" final project assignment PDF (Acrobat (PDF) 321kB Aug15 24)

GPS Strain Calculators: your instructor will tell you which of these to use.



     

This module is part of a growing collection of classroom-tested materials developed by GETSI. The materials engage students in understanding the earth system as it intertwines with key societal issues. The collection is freely available and ready to be adapted by undergraduate educators across a range of courses including: general education or majors courses in Earth-focused disciplines such as geoscience or environmental science, social science, engineering, and other sciences, as well as courses for interdisciplinary programs.
Explore the Collection »