How to use the online seismometer
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Step 1: Put your phone flat, screen up, on a solid floor. The ground floor or basement is best, on tile or concrete, away from walking paths.
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Step 2: Plug it in if you plan to leave it running, and set auto-lock to Never so the screen stays on.
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Step 3: Tap "Start". On iPhone, tap Allow when Safari asks for Motion & Orientation access.
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Step 4: Step away. The trace scrolls across the screen and shows the last 60 seconds. Your own footsteps show up clearly, so stay back for a clean trace.
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Step 5: If you feel shaking, note the time and the Peak since start reading. Tap Reset peak afterwards so the next event starts fresh.
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Step 6: A few minutes later, check the USGS latest earthquakes map to see if a real earthquake was recorded near you.
An online seismometer can’t replace a real seismic station, but it can answer the question you have right after something shakes: was that an earthquake, or just a truck? This page turns your phone’s motion sensor into a seismograph. It draws the shaking as a scrolling line, shows the peak acceleration in g, and gives a rough shaking intensity based on the scale the USGS uses.
This is not an earthquake warning system
This page won’t warn you before shaking arrives, and it doesn’t alert anyone. It only shows what your phone feels, as it happens. For real warnings on the West Coast, the USGS runs ShakeAlert. If you feel strong shaking, drop, cover and hold on first. Look at your phone later. Once the shaking stops, check for damage and the smell of gas before you move around.
From peak acceleration to shaking intensity
Magnitude is the size of an earthquake at its source. Intensity is how hard the ground shook where you are. Your phone can only estimate intensity at its own spot. The table shows how USGS ShakeMap (Wald and others, 1999) links peak ground acceleration to the Modified Mercalli intensity scale. The phone shows peak acceleration in g, so both are listed.
| Peak acceleration (% g) | Peak acceleration (g) | Intensity | Perceived shaking |
|---|---|---|---|
| Below 0.17 | Below 0.0017 | I | Not felt |
| 0.17 to 1.4 | 0.0017 to 0.014 | II to III | Weak |
| 1.4 to 3.9 | 0.014 to 0.039 | IV | Light |
| 3.9 to 9.2 | 0.039 to 0.092 | V | Moderate |
| 9.2 to 18 | 0.092 to 0.18 | VI | Strong |
| 18 to 34 | 0.18 to 0.34 | VII | Very strong |
| 34 to 65 | 0.34 to 0.65 | VIII | Severe |
| 65 to 124 | 0.65 to 1.24 | IX | Violent |
| Above 124 | Above 1.24 | X and up | Extreme |
Treat the intensity as a rough guide. The table was built from recordings at seismic stations, not from phones on house floors. A floor in a house, especially upstairs, can move more than the ground under it. A door slam or footsteps near the phone can push the reading up several steps for a moment, even though no earthquake happened.
Common causes and fixes
Most shaking that makes people ask “was that an earthquake?” has a local cause. The shape of the trace helps you tell them apart.
- Trucks and buses. Shaking builds and fades over a few seconds as the vehicle passes, and it repeats with traffic.
- Trains. Steady shaking for as long as the train takes to pass, often a minute or more.
- Construction and quarry blasts. Repeated jolts during working hours. Blasts are single sharp events, often at about the same time each day.
- Sonic booms and thunder. A sharp bang that rattles windows. The pressure wave shakes the house briefly.
- Your own house. Footsteps, doors, a washer on spin, or the furnace starting up.
- Earthquakes. A sudden start, sometimes a sharp jolt followed by rolling, lasting from a few seconds to a minute or more. Many people nearby feel it at the same moment.
For a cleaner trace, use the lowest floor, set the phone on concrete or tile, and keep it away from appliances and walking paths. If something shakes your house again and again, the house vibration logger records each event with its time.
What this tool can’t measure
- Magnitude, location or depth. Only networks of seismic stations can work those out.
- Small or distant earthquakes. A phone sensor is far noisier than a real seismometer. It only picks up shaking you could probably feel.
- Very slow motion. Large, distant earthquakes can make slow rolling waves that take a second or more per sway. The phone measures this poorly.
- Fast vibration. Phones deliver about 60 samples per second, so they can’t measure much above 30 Hz.
- Time while paused. Nothing is recorded while the screen is locked or the page is in the background.
Phone readings are a good guide, not a certified measurement. For more on the limits, read how accurate a phone vibration meter is.
Frequently asked questions
Was that an earthquake?
Check the USGS latest earthquakes map. Earthquakes in the US usually appear there within minutes, though small ones can take longer. If nothing shows up and the shaking was short and sharp, a truck, train, blast or sonic boom is more likely.
Can my phone detect earthquakes?
Only ones strong enough to feel where you are. A phone sensor is far noisier than a real seismometer, so small or distant earthquakes are lost in its noise. Networks of seismic stations run by the USGS and its partners do that job.
What's the difference between magnitude and intensity?
Magnitude measures the size of an earthquake at its source, with one number per quake. Intensity describes how strong the shaking was at a given place, so it changes with distance and ground. This page estimates a rough intensity at your phone, never the magnitude.
Will this warn me before an earthquake?
No. It shows shaking as it happens, and it doesn't send alerts. In California, Oregon and Washington, the USGS ShakeAlert system provides earthquake early warnings. When shaking starts, drop, cover and hold on.
Why does the trace jump when I walk by?
Your footsteps are close to the phone, so they shake the floor under it more than most distant sources. Stay a few steps away, keep pets off the floor nearby, and use the lowest floor for the quietest trace.
How do I report shaking I felt?
Use the USGS Did You Feel It? form. Reports from people help map how strongly an earthquake was felt in different places.
Last updated .