Earthquake & Seismic Wave Laboratory
Trigger a virtual earthquake, watch P, S and surface waves radiate outward, read live seismograph traces at three stations, and triangulate the epicenter from S−P intervals.
How to use: click the map to set the epicenter, choose magnitude/depth/fault type, then press Trigger earthquake to watch P, S and surface waves ripple out and the seismograph traces record at each station. Try the challenges to locate the epicenter and assess tsunami risk.
Each station's S−P interval (the time gap between the S wave and P wave arriving) tells you its distance from the epicenter: distance (km) ≈ S−P interval (s) × 8. Click on the map where you think the epicenter is, then check your estimate.
Challenge 2: engineer a tsunami-risk earthquake
Shallow, large offshore earthquakes are the ones that generate tsunamis. Set magnitude to 7.5 or higher and focal depth to 30 km or shallower, then check.
About the Earthquake & Seismic Wave Laboratory
Free earthquake & seismic wave laboratory. Trigger a virtual earthquake, watch P, S and surface waves radiate outward, read live seismograph traces at three stations, and triangulate the epicenter from S−P intervals. Drag, change the sliders and see the result live. No sign-up, works on phone and computer. Built for geology, the earthquake & seismic wave laboratory runs instantly in your browser: change a setting or drag an object and the result updates at once, so you learn by trying things out rather than only reading about them.
Trigger a virtual earthquake, watch P, S and surface waves radiate outward, read live seismograph traces at three stations, and triangulate the epicenter from S−P intervals. Use it to explore geology ideas at your own pace, then check what you found against the key ideas further down this page.
How to use the Earthquake & Seismic Wave Laboratory
- Use the controls to change Magnitude, Focal depth, Fault type. The simulation reacts instantly.
- Press "Trigger earthquake", "Reset", "Reset to defaults", "📄 Lab Report" to start, reset or change what is happening.
- Where you see a glowing handle, object, weight or atom, drag it with your mouse or finger. Everything responds in real time.
- Watch the readouts and graphs update as you experiment, and compare what you see with the key ideas below.
Things to try
- Trigger a magnitude 7 earthquake and read the S−P interval at each station.
- Convert each interval to a distance and try to triangulate the epicenter on the map.
- Change the focal depth and see how it changes arrival times.
- Compare a shallow versus deep earthquake of the same magnitude.
Key ideas you can learn
- P waves travel fastest and arrive first; S waves are slower; surface waves are slowest but usually cause the most damage.
- The S−P time interval at a station grows with distance from the epicenter.
- Distance (km) ≈ S−P interval (seconds) × 8 is a widely used quick estimate.
- Three stations' distance circles intersect at the true epicenter (triangulation).
Where this is used in the real world
The USGS and seismic networks worldwide use this exact S−P triangulation technique, now automated, to report earthquake locations within minutes.
Who is this simulation for?
Students, teachers and curious learners of all ages.
For teachers: project it on the board, let students predict what will happen, then run it together. For students: change one thing at a time and write down what changes.
Frequently asked questions
Why do seismologists need at least three stations to locate an epicenter?
One station's S−P interval only gives a distance, forming a circle of possible locations; three circles from three stations intersect at a single point, the epicenter.
Why do surface waves cause the most damage despite arriving last?
They travel only along the Earth's surface, so their energy spreads out in two dimensions instead of three, keeping amplitudes larger over distance.
Is the Earthquake & Seismic Wave Laboratory free to use?
Yes. It is completely free, with no signup, no download and no ads inside the simulation. It runs in your web browser.
Does the Earthquake & Seismic Wave Laboratory work on a phone or tablet?
Yes. It uses touch as well as the mouse, so you can drag objects with your finger. A larger screen makes the controls easier to see.