How does an earthquake early warning system work?
An earthquake warning system uses existing seismic networks to detect moderate to large earthquakes. Computers, communications technology, and alarms are devised to notify the public while an earthquake is in progress. This is not the same as earthquake prediction. Data from the 2011 Tohoku, Japan earthquake taught us much about mega-thrust earthquakes. In its simplest form, an earthquake early-warning system assumes the earthquake results from sudden slip on a small area of a fault surface, and the initial magnitude represents that motion. But for earthquakes greater than magnitude 7, that small patch at the epicenter is just the starting point for a rupture that spreads over a huge area as it tears the fault and radiates immense seismic energy. In this animation we can see how ground motion, measured by GPS, can enhance earthquake early warning.
This animation was made by UNAVCO in collaboration with the Cascadia EarthScope Earthquake & Tsunami Education Program CEETEP and IRIS. The animation with related resources can be found on the UNAVCO site.
- Earthquakes cannot be predicted, but once one has occurred there is a warning period until the waves arrive in an off-shore subduction-zone event
- Mega-thrust earthquakes are often just the beginning of a larger fault that continues to release
- Even 10 seconds warning can give someone time to get to a safe location