Earthquake Epicenter Triangulation Lab | P- and S-Wave Investigation

The Description

Find the difference between P- and S-wave arrival times. Read the travel-time graph. Draw a few circles. Voilà—earthquake epicenter! Except one student is reading the graph backward, another is measuring from the wrong spot, and someone has asked “Is this right?” approximately 47 times. Sound familiar?

This 2–3 day epicenter triangulation lab breaks a surprisingly fiddly process into a sequence students can actually follow: seismic waves, graphs, distances, scales, and finally compass triangulation. The science stays challenging; the materials stop getting in the way.

What Students Will Do

Students determine P–S arrival-time differences, interpret seismic travel-time graphs, calculate earthquake distances, practice map scales and compass circles, and triangulate epicenters using multiple stations. Embedded self-checks encourage them to spot and revise their own errors before moving on. Students also connect earthquake monitoring to ShakeAlert and real-world hazard response.

Why This Resource Is Different

I begin with nice, clean whole-thousand-kilometer distances for a reason. First, students figure out why the process works; then distances such as 1,280 kilometers make precision matter. The steps haven't changed. The precision has. The built-in checks help replace the chorus of “Is this right?” with “Wait, I see what I did.” Pair it with the Sumatra Tsunami Investigation to turn those newly located epicenters into evidence for a larger mystery.

What's Included?

• Student investigation workbook, seismic data tables, and maps

• Earthquake triangulation mapping activities

• P- and S-wave travel-time notes

• Additional calculation practice and embedded self-checks

• Complete teacher answer keys

• Two editable assessments, including a parallel version

The Details

Approximately 2–3 class periods; middle and high school Earth Science. Skills: P- and S-wave arrival times, travel-time graphs, distance calculations, map scales, compass triangulation. NGSS connections: MS-ESS3-2 and MS-PS4-1; practices include analyzing data and mathematical thinking. You bring the students. I'll bring the carefully organized circles.