Free planning tool

How many earthquake sensors does your area actually need?

Place sensors on the map, drop an earthquake on it, and see whether the network would have detected it — or stayed silent. Nothing is saved, and you do not need an account.

Click the map to place your first sensor. A GeoShake station appears where you click.

X and Facebook post the link, not the image — save it first.

Scenarios

Two layouts, same five sensors:

Or replay a real earthquake. Your sensors move there if they are far away, so you can see the result straight away.

On the map

GeoShake sensors 0 Click to add, click one to remove. Three minimum — that is the threshold for publishing an event.
Test earthquake Drag it where the shaking starts.
Your location not set Never leaves your browser.

Warning time

Place your location above and this fills in.

Place at least one sensor

Click anywhere on the map. Then set the magnitude and see what the network would do.

Earthquake

Detected within—
Nearest sensor—

Your sensors — 0

No sensors yet.

Finds the arrangement that covers the most ground for M4.0 events — a network is designed around the smallest earthquake you want to catch; bigger ones come free. Turn on Past earthquakes first and it will favour the places that actually shake.

Takes the network you have already placed and finds the single spot that unlocks the most new ground.

Why three sensors, and not one

GeoShake does not publish an earthquake because a single sensor shook. Shaking has many causes — a lorry, a slammed door, someone moving the shelf the sensor sits on. The network only publishes an event when at least three sensors register it within seconds of each other, with arrival times consistent with a P-wave travelling at 6 km/s.

That one rule is why placement matters more than count. Five sensors clustered in a valley behave completely differently from five spread across a region — same hardware, same money, very different networks. Try the two examples above.

What the tool assumes

Detection range grows with magnitude. The tool uses:

The cap matters: the bare formula would put an M8.8 at over 2,000 km, which is nonsense. Very distant large earthquakes arrive as long, slow ground motion that a consumer accelerometer cannot separate from ordinary building movement.

These are engineering estimates, not measurements. We have never had a network dense enough to measure our own detection curve — as of today our three live sensors are all within a few hundred metres of each other. The first real measurement will come from the first dense cluster somebody deploys. When we have it, this tool changes and we will say so.

The model also ignores depth, soil conditions and directionality, all of which matter in reality. It is a planning aid for geometry, not a hazard assessment. And it is deliberately optimistic about warning time: it assumes zero processing and network delay, so treat any figure it gives as a ceiling.

Privacy

Your sensor positions stay in your browser. We do not store them, and there is no account or cookie behind this page. We do count how many people plan a network in each region, rounded to a roughly 10 km grid before anything is written down — enough to know where coverage is wanted, never enough to locate anyone.

If the answer surprised you

Most people find they need more sensors than they expected, arranged more tightly than they expected. That is the honest shape of the problem: density buys warning time, and a thin network buys very little.

If you are planning coverage for a town, a campus or a region and want a second pair of eyes on it, write to us. We will model it properly — what your layout would catch, what it would miss, and whether a different arrangement of the same budget does better. No charge, no obligation.

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