EARTHQUAKE FIELD GUIDE
A few useful answers.
Read a report, understand its limits, and choose your alerts.
Magnitude, depth or intensity?
Magnitude measures source size. Depth locates the source below the epicenter. Intensity describes local shaking, which varies between places.
See the scales explained →Why do reports change?
New measurements refine magnitude, location and depth. “Reviewed” means the reporting network has checked the event; later revisions are still possible. Missing values mean unavailable, not zero.
We check the daily USGS feed every two minutes and older revisions every ten minutes. Catch-up can take longer after interruptions. Each event links to its USGS source.
Does the map include every earthquake?
No. It shows reports stored here for the selected time window. Regional views use geographic boxes and may include neighboring areas. Nearby events are not automatically aftershocks.
Search the USGS historical catalog ↗How do earthquake notifications work?
Set minimum magnitude and maximum distance in Forecast Bar, or use Auto mode. A qualifying Pro or Gold subscription is required.
Notifications follow detected events; they are not predictions or early warnings before shaking. Delivery depends on your device, connection and settings.
Earthquake alert settings →Where should I check safety and tsunami information?
If you feel shaking, drop, cover and hold on. Follow local emergency instructions. A tsunami flag on an earthquake report does not establish that a warning is in effect.