Guide
Reading live earthquake data
The map shows earthquakes that have already happened, reported by the US Geological Survey. Here is what the numbers mean and what they cannot do.
Where the data comes from
The earthquakes on the globe come from the USGS summary feeds, which the USGS describes as updated every minute. The feeds cover the past hour, day, 7 days and 30 days. The USGS says information it authors is in the US public domain and asks for credit; the app shows the source on every card.
Alert levels
For larger earthquakes the USGS publishes PAGER alerts. By the USGS's background page, the fatality thresholds for yellow, orange and red alerts are 1, 100 and 1,000. For economic loss, red is 1 billion US dollars or more, orange is 100 million to 1 billion, and yellow is 1 to 100 million. PAGER combines the shaking map with a population database to estimate how many people were exposed to each level of shaking.
When the shaking arrives
The app can show how long seismic waves would take to reach you from a given earthquake. It uses a simple model: P waves at 8.0 km/s and S waves at 4.5 km/s along a straight path. Those are upper mantle speeds, and the model is not a real Earth model. In one check against a published travel-time example, our times were about 30 percent too long, so treat the numbers as an illustration of the idea, not a measurement.
What nobody can do
This site does not predict earthquakes, and no listing on it should be read as a prediction. The USGS says that nobody has predicted a major earthquake. What the app can do is show you what has just happened and what is near you.
Sources
- USGS earthquake GeoJSON feeds. Summary feeds updated every minute
- USGS PAGER background. Alert levels
- USGS: Can you predict earthquakes?. Re-read before relying on it; the wording was last checked in our research notes