GETSI Teaching Materials >GPS, Strain, and Earthquakes > Unit 5: 2014 South Napa Earthquake and GPS strain
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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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Unit 5: 2014 South Napa Earthquake and GPS strain

Vince Cronin, Baylor University (
Phil Resor, Wesleyan University (
Author Profile

These materials have been reviewed for their alignment with the Next Generation Science Standards as detailed below. Visit InTeGrate and the NGSS to learn more.


Students analyze and interpret data from the 2014 South Napa, California, earthquake to calculate.

Science and Engineering Practices

Using Mathematics and Computational Thinking: Use mathematical, computational, and/or algorithmic representations of phenomena or design solutions to describe and/or support claims and/or explanations. HS-P5.2:

Obtaining, Evaluating, and Communicating Information: Critically read scientific literature adapted for classroom use to determine the central ideas or conclusions and/or to obtain scientific and/or technical information to summarize complex evidence, concepts, processes, or information presented in a text by paraphrasing them in simpler but still accurate terms. HS-P8.1:

Developing and Using Models: Develop and/or use a model (including mathematical and computational) to generate data to support explanations, predict phenomena, analyze systems, and/or solve problems. HS-P2.6:

Analyzing and Interpreting Data: Analyze data using tools, technologies, and/or models (e.g., computational, mathematical) in order to make valid and reliable scientific claims or determine an optimal design solution. HS-P4.1:

Cross Cutting Concepts

Stability and Change: Much of science deals with constructing explanations of how things change and how they remain stable. HS-C7.1:

Stability and Change: Change and rates of change can be quantified and modeled over very short or very long periods of time. Some system changes are irreversible. HS-C7.2:

Patterns: Mathematical representations are needed to identify some patterns HS-C1.4:

Cause and effect: Cause and effect relationships can be suggested and predicted for complex natural and human designed systems by examining what is known about smaller scale mechanisms within the system. HS-C2.2:

Disciplinary Core Ideas

Natural Hazards: Natural hazards and other geologic events have shaped the course of human history; [they] have significantly altered the sizes of human populations and have driven human migrations. HS-ESS3.B1:

Performance Expectations

Earth and Human Activity: Analyze and interpret data on natural hazards to forecast future catastrophic events and inform the development of technologies to mitigate their effects. MS-ESS3-2:

Engineering Design: Analyze a major global challenge to specify qualitative and quantitative criteria and constraints for solutions that account for societal needs and wants. HS-ETS1-1:

This material was developed and reviewed through the GETSI curricular materials development process. This rigorous, structured process includes:

  • team-based development to ensure materials are appropriate across multiple educational settings.
  • multiple iterative reviews and feedback cycles through the course of material development with input to the authoring team from both project editors and an external assessment team.
  • real in-class or field camp/course testing of materials in multiple courses with external review of student assessment data.
  • multiple reviews to ensure the materials meet the GETSI materials rubric which codifies best practices in curricular development, student assessment and pedagogic techniques.
  • created or reviewed by content experts for accuracy of the science content.

This page first made public: Dec 9, 2016


The 2014 South Napa earthquake was the first large earthquake (Mag 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 more than $400 million in damages. This activity uses a single triangle of GPS stations (P198, P200, SVIN), located to the west of the earthquake epicenter, to estimate both the interseismic strain rate and coseismic strain. By the end of the exercise, the students also have direct evidence that considering the recurrence interval on a single fault, which is part of a larger system, is not reasonable. An extension option gives the opportunity to discuss earthquake early warning systems.

Note: Although the term GPS (Global Positioning System) is more commonly used in everyday language, it officially refers only to the USA's constellation of satellites. GNSS (Global Navigation Satellite System) is a universal term that refers to all satellite navigation systems including those from the USA (GPS), Russia (GLONASS), European Union (Galileo), China (BeiDou), and others. In this module, we use the term GPS even though, technically, some of the data may be coming from satellites in other systems.

Learning Goals

Unit 5 Learning Outcomes

Unit 5 Teaching Objectives

  • Affective: Encourage reflection and analysis of societal impacts of earthquakes.
  • Cognitive: Facilitate students' ability to compare interseismic strain with coseismic displacements.

Context for Use

This module was designed for structural geology courses but can also be successfully used in geophysics, tectonics, or geohazards courses or possibly even a physics or engineering course seeking practical applications. Unit 5 assumes that students have already learned to use and analyze results from a GPS Strain Calculator and thus must come after Unit 3: Getting started with GPS data and Unit 4: GPS and infinitesimal strain analysis. In fact, Unit 5 could even be done after Unit 6: Applying strain and earthquake hazard analyses to different regions, which is the summative assessment for the rest of the module (Units 1–4). We have found the 2014 South Napa earthquake example can be a great way to return to and solidify these concepts later in the course and to bring up again the critical importance of understanding ongoing to strain in preparing our society for earthquake hazards.

Description and Teaching Materials

Primary exercise

This exercise helps foster analysis and discussion of the Mw 6.0 August 24, 2014, South Napa earthquake using data from permanent GPS arrays. The information provided could be presented as: (1) an instructor-led discussion or (2) part of a student-centered activity building on the GPS strain analysis process. Use the full resources provided to do the student-centered activity. For the discussion-only option, have the students still do the short homework assignment to learn about the 2014 South Napa earthquake, but then primarily use the presentation to guide a class discussion of the analysis.

We suggest leading this exercise with a short homework assignment in which the students are asked to come to class having gathered data about the 2014 South Napa earthquake. This short pre-assignment is also on slide #2 of the presentation.

  • In preparation for the next lab period, each student should select an aspect of the 2014 South Napa earthquake for which to do some research: seismology, faulting, or damage (pass around a signup sheet with three columns and only enough spaces so that you get an even distribution of topics in the class)
  • Come to class ready to serve as the "expert" on your select topic for your three-person team
  • READ the short background document that was emailed to you

Once in class, run a quick jigsaw activity in which the class is divided into groups of three, with one of each type of "expert." Each student is responsible for bringing the entire team up to speed on the topic she or he researched.

Below are the teaching materials for the unit:

Extension Option—Earthquake Early Warning System

As of 2015, Japan and Mexico have public-alert earthquake early warning systems that can sense initial shaking in one region, identify that an earthquake is underway, and send notices within tens of seconds to people and infrastructure further away that imminent shaking can be expected. The United States does not currently have a fully functional earthquake early warning system, but a prototype has been developed for the Bay Area, called ShakeAlert. It was in operation during the 2014 South Napa earthquake and functioned correctly to send a warning, for example, to the BART (Bay Area Rapid Transit) trains. In happened that no trains were moving because the earthquake occurred in the middle of the night, but had it been daytime, trains would have been slowed or stopped by the time shaking arrived in San Francisco. You can ask students, what types of earthquake risk could be reduced by having 10–100 seconds of warning? After a short discussion, you could then show them the short animation about the ShakeAlert system.
Youtube: ShakeAlert—Earthquake Early Warning. How does it work?
MP4 file: ShakeAlert—Earthquake Early Warning. How does it work? (MP4 Video 26MB Oct7 15)

Teaching Notes and Tips

  • The pre-activity homework provides excellent motivation for the activity, but instructors may need to limit discussion to complete the activity in a single class meeting.
  • Instructors wishing to complete the activity in a single class session may want to have students plot the velocity/offset and strain rate / strain data in advance or provide the plotted data to students so that they can focus on interpretation of the data.
  • The conclusion of the activity is an assessment of earthquake recurrence using GPS observations of interseismic and coseismic deformation.
    • Instructors may want to revisit the Tohoku earthquake using slide 7 from Unit 4 Example interseismic data from Japan (PowerPoint 2007 (.pptx) 11.8MB Dec7 16) to help students develop their understanding of elastic rebound.
    • Physical analogs such as spring-slider models (for example: may also be helpful in developing student intuition.
    • Unit 5 2014 South Napa earthquake presentation (PowerPoint 2007 (.pptx) 29.3MB Dec8 16) slides 22–30 are provided to foster discussion of the earthquake cycle using data from the South Napa earthquake.
    • The simple model used in the activity results in an unrealistically short recurrence interval. Unit 5 2014 South Napa earthquake presentation (PowerPoint 2007 (.pptx) 29.3MB Dec8 16) slides 31–32 are provided to guide discussion of two major shortcomings of the model. Instructors may want to couch this discussion as an example of how we can learn from the failure of models. State-of-the-art earthquake rupture forecasts use GPS data and elastic rebound theory to estimate earthquake probabilities, but incorporate more realistic fault geometries and other underlying assumptions into their models.
  • We provide supporting math materials in Unit 2 for instructors interested in having student take the quantitative analysis to a deeper level. These include vector, matrices, and infinitesimal strain analysis background.


Formative Assessment:

Observation of student activity and conversations, individual questioning, and group discussion are excellent ways to conduct formative assessment as the students complete this exercise.

Summative Assessment:

The student exercise is the summative assessment for this unit. Many of the questions have definite right or wrong answers. To receive full credit, students must show their work, where appropriate. Where an open-ended answer is required, students are assessed based on a simple 2-point system.
2 points = correct answer with thorough supporting evidence and/or complete description
1 point = answer not completely correct or lacking thorough supporting evidence or description
0 points = incorrect answer

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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.
Explore the Collection »