Earthquake Lab
Locating an epicenter from three seismograms is one of the most common labs in middle school earth science, and it is nearly always done on photocopies. Earthquake Lab keeps the method, every step of it, and adds what paper cannot: waves that move, a different hidden quake for every student, and a check that says which step went wrong.
Using this with a class? Make a free class and add your students yourself: each gets a username and password, with no email or Google account needed. Or give them one join code. Using Google Classroom? Post the link there; with a free class, the link also puts each student in your class, so you see their work. mytekDev is also available from the Google Workspace Marketplace, so your school's Google admin can install it for everyone.A first lesson: One period: draw a fault, break it, and watch the gap between the P and S waves grow with distance. A second period: Find a quake, the worksheet from marking the arrivals to drawing the circles, with the check and the sheet.
Set up a free class Share to Google ClassroomWhat a student actually does
A made-up region, 700 kilometers across, with a coast, mountains, nine towns and three seismograph stations. The student drags across the map to draw a fault, chooses how it moves (slide past, pull apart, push together), how deep it breaks and how big it is, and presses Break the fault. Two rings leave the star together: the fast P wave and the slower S wave. Under the map each station's pen writes its seismogram: a twitch when the P wave arrives, a bigger swing when the S wave does, then the surface waves. The farther the station, the bigger the gap between the twitch and the swing, about 8 kilometers for every second, and the bench counts it.
Hide a quake and find it is the worksheet. A quake breaks where the student cannot see it, and three seismograms are all they get. They drag a P flag and an S flag to where each wave starts, subtract to get the gap, slide a strip of paper along the travel-time chart to read the distance, and set a drawing compass against the map's ruler to swing a circle round each station. Where the three circles cross, they click, and press Check. The app shows the real star, says how far off the click was, and if it missed, which step most likely went wrong: the surface waves marked as the S, a chart read in the wrong place, a circle round the wrong station.
After a break, The towns shows how hard each town shook, from not felt to extreme, and how many seconds of warning it could have had once the nearest station felt the P wave. A fault under the sea, big enough, sends a tsunami across the map's own sea floor, in minutes rather than seconds. Past quakes plays a hundred years of earthquakes onto the map, and they line up along a few faults. At high school the student also works out when the quake happened and its magnitude, with Richter's own nomogram.
A hidden quake, ready to check. Each circle is one station's distance, read off the travel-time chart from the gap between its P and S flags. The three circles cross at one spot, near Port Maren: the epicenter.
What they are learning while they work
Nothing here is presented as a lesson. This is what the activity is made of.
| What the student does | What it is |
|---|---|
| Watches two rings leave the star together and pull apart | P waves and S waves. Both waves start at the same moment. The P wave travels about 6 kilometers a second and the S wave about 3.5, so the S wave falls further behind the farther they go. |
| Drags a station farther away and breaks the fault again | The S-P gap as a distance. The gap between the two arrivals grows about one second for every 8 kilometers. Like counting from lightning to thunder, it says how far away the quake was, not which way. |
| Slides the paper strip up the travel-time chart | Reading a travel-time chart. The chart's two lines are the two waves' times for each distance. The place where the gap fits between them is the distance. |
| Draws one circle, then a second, then a third | Triangulation. One distance puts the quake somewhere on a circle. Two circles cross in two places. The third circle passes through only one of them. |
| Opens the side view under the star | Focus and epicenter. The fault breaks underground at the focus. The epicenter is the point on the map straight above it. Because the waves start below the map, the circles come out a little too big. |
| Compares the towns' shaking after one quake | Magnitude and intensity. A quake has one magnitude, its size. Each town has its own shaking, and it is weaker the farther away the town is. |
| Moves a station next to the fault and watches the warnings grow | Earthquake early warning. An alert goes out once the nearest station feels the fast P wave, ahead of the strong S wave. It is not a prediction: nobody can say ahead of time when a quake will come. |
| Turns on Past quakes and watches a hundred years go by | Where earthquakes happen. Quakes are not spread evenly. They line up along faults, the same lines break again and again, and small ones far outnumber big ones. |
How to tell whether it landed
Ask, and let them show you. A student who has understood it can answer these without help.
- One station had the biggest gap between its P wave and its S wave. What does that tell you about that station?
- A station records a gap of 20 seconds. About how far away was the quake, and how did you work it out?
- Why do you need three stations to find an epicenter? What would one tell you? Two?
- Your three circles left a small triangle instead of one point. Give two reasons.
- The town nearest the quake got no warning, and a town far away got many seconds. Why?
- Nobody can say what day an earthquake will happen. What can scientists say ahead of time?
Use it in your subject
Not a technology class? Then the app is how students show what they learned in your unit. More projects for every subject.
Middle school earth science
MS-ESS3-2 most directly: data on natural hazards, the locations and sizes of quakes, and seconds of warning as a technology that lessens their effects. MS-ESS2-2 for earthquakes as sudden events in slow processes, and MS-ESS2-3 for quakes lining up along faults. No NGSS performance expectation names locating an epicenter; it is the classroom's way of doing the data work they ask for.
Physical science
MS-PS4-1: two waves with different speeds, and amplitude that grows about ten times for each step of magnitude. The gap is distance divided by speed, worked out twice.
Elementary science
4-ESS2-2, the pattern of earthquakes on a map, with Past quakes; 4-ESS3-2, reducing the impacts of earthquakes and tsunamis. The fourth grade level makes quakes and watches; it does not ask for the chart or the compass.
High school earth science
HS-ESS2-3: what seismic waves tell us about the inside of the Earth. The high school level adds when the quake happened, from the chart, and its magnitude, from the tallest swing and Richter's nomogram.
Practical notes
- AgesGrades 6 to 8 are the home ground. Setup has a fourth grade level, which makes quakes, reads the towns and watches past quakes without the worksheet, and a high school level that adds origin time and magnitude.
- TimeOne period to make quakes and watch the gap grow. A second for Find a quake and the sheet. The first find takes most of that period; the second goes much faster.
- EquipmentA computer or Chromebook with a modern browser. Nothing to install, no drawing compasses, no photocopies. A projector works well for the first break with the whole class.
- CostFree. The app has no paid tier.
- PrepAbout fifteen minutes: break one fault and open The towns, then find one hidden quake yourself, all five steps and the check. That is the whole arc of the two periods.
- In a groupOpen Setup in the app's header: the level, whether every student gets their own hidden quakes or the class shares the same ones, which questions are on the sheet, up to ten of your own, and a printed answer key.
For co-ops, microschools, and classrooms
Set it up once in Setup and hand the project out as the starter; the setup travels with it. With each student's own quakes no two answers match, so answers cannot be passed along, and the app checks every one. With shared quakes the whole class hunts the same ones in the same order, and you can go over one together. Students can also hide a quake for a friend, and whoever opens the project hunts it.
Common questions
Is it free?
Yes. Earthquake Lab has no paid tier, and it can be tried right on this page without an account.
Does it replace the paper epicenter lab?
It is the paper lab, step by step: the student marks the arrivals, subtracts, reads the chart and draws the circles. The app never snaps a flag to the right place or does a step for them. What it adds is the waves moving, a different quake for each student, and a check that names the step that went wrong.
How real are the numbers?
The waves travel at 6 and 3.5 kilometers a second, typical for the top of the Earth's crust, so the gap grows about one second for every 8.4 kilometers; the classroom rule of about 8 is accepted. The magnitude comes from Richter's 1935 formula for Southern California, the shaking at the towns from a relation fit to California quakes (Bakun and Wentworth, 1997), in the words USGS uses for each level, and the tsunami's speed from the depth of the water, the way NOAA works it out.
What does it simplify?
The map is made up, and so is every quake on it. The waves travel in straight lines through one kind of rock; in the real Earth they speed up with depth and bend, which is why the 8 km rule holds best within about 200 kilometers. How deep a quake breaks does not change the towns' shaking here, though a deeper quake usually shakes the ground above it less. The warning comes from one station, where real systems use several. The tsunami has no heights in meters, no flooding and no damage.
Why can the magnitude slider go to 8?
So a quake under the sea can reach the sizes that make a destructive tsunami. Richter's formula, which the high school level reads magnitude with, holds below about magnitude 7 and within a few hundred kilometers; the hidden quakes stay inside that, and the help says seismologists now report moment magnitude.
Does it run on Chromebooks?
Yes. It runs in the browser with nothing to install. The flags, the paper strip and the compass work with a mouse, a trackpad or a finger, and the arrow keys nudge the last flag a tenth of a second.
Is there a grade level setting?
Yes, in the header and in Setup: fourth grade, middle school and high school. Each changes what the app asks for and which questions are on the sheet.
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Where to go next
Lesson plans
4 ready-to-teach class periods with a teacher plan, a student worksheet, an exit ticket with answers, and the standards it meets.
Start with Earthquake Lab
Trying it costs nothing and takes about five minutes. An account is what makes the work last.
Earthquake Lab is one of the making apps on the platform. Its map is a made-up region 700 by 300 kilometers, the ruler under it runs to 450 kilometers, and a find within 15 kilometers of the real epicenter counts as a good one.
Page last reviewed November 2026.
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