# Earthquake Magnitude: How Can We Compare the Sizes of Earthquakes?

This material was originally developed by Spreadsheets Across the Curriculum as part of its collaboration with the SERC Pedagogic Service.

#### Summary

In this Spreadsheets Across the Curriculum activity, students create spreadsheets and graphs to explore earthquake magnitude, wave amplitude, and energy release. In particular, students will realize that the magnitude scale is logarithmic. Because each step in magnitude represents a 10-fold increase in wave amplitude and approximately a 30-fold increase in energy release, large earthquakes are much more powerful than small earthquakes. This is a self-paced activity in which students follow a PowerPoint presentation to create spreadsheets and graphs using Excel.

## Learning Goals

The key quantitative concept is logarithms. Additional quantitative concepts include scientific notation, ratios, and linear and semilogarithmic graphs. The fundamental concept within seismology is the scale of earthquake magnitude and energy release. In particular, students come to grasp how large a large earthquake really is.

## Context for Use

Equipment: Each student or pair of students needs a computer with Excel and PowerPoint.

Classes: I have used this module in a Structural Geology and a Solid Earth Geophysics course with upper level undergraduates. Each class had fewer than 20 students. I intended the module for introductory geoscience courses, but have yet to use it myself in a freshman-level class.

In the Structural Geology class, students worked in pairs during lab to complete the module. All finished within 2.5 hours. I provide a handout of the whole PowerPoint file with six slides per page. Under select slides I wrote, "Show Me" with a square next to it. As students finished tasks on those slides, they showed me their work and I initialed the square. Students received perfect scores if they completed the exercise. This worked well for sophomore to senior level students with varying Excel skills.

In the Solid Earth Geophsics class, I assigned the module as homework. Students turned in hard-copies of the Excel spreadsheets and graphs. This worked well for junior and senior level students with excellent quantitative skills.

## Description and Teaching Materials

PowerPoint SSAC2005:QE531.LRW1.1-Student (PowerPoint 285kB Feb15 07)

If the embedded spreadsheets are not visible, save the PowerPoint file to disk and open it from there.

This PowerPoint file is the student version of the module. An instructor version is available by request. The instructor version includes the completed spreadsheet. Send your request to Len Vacher (vacher@usf.edu) by filling out and submitting the Instructor Module Request Form.

## Teaching Notes and Tips

I found that many students are highly resistant to using Excel and doing math in a non-math class. To overcome this predisposition, I now typically ask the students to work in pairs and complete the module in class or lab. Another strategy would be to have students begin the module in class, but to complete it at home.

I need to remind students that they should use pencil and paper to rearrange equations as they work through the module. In many cases, students assume that, because they are working with a computer, all their work will be done on the computer.

Because students' Excel skills vary, I provide a single sheet of Excel pointers when students work on the module. It contains tips such as using equal signs at the beginning of formulae, ^ for exponents, etc.

## Assessment

I typically give anonymous pre- and post-tests to assess student learning from the modules. These tests ask about familiarity with Excel as well as other quantitative skills.

## References and Resources

Online educational resources on seismology
The Incorporated Research Institutes of Seismology (IRIS): IRIS Education and Outreach

Online educational resources on quantitative skills in geology
Digital Library of Earth Science Education (DLESE): Teaching Quantitative Skills in the Geosciences.