Earthquake early warning system

"Earthquake Early Warning" redirects here. For the system in the United States, see ShakeAlert. For the system in Japan, see Earthquake Early Warning (Japan). For the system in Mexico, see Mexican Seismic Alert System.
"EEW" redirects here. For the epoxy equivalent weight, see Epoxy value.
An animation detailing how earthquake warning systems work: When P-waves are detected, the readings are analyzed immediately, and, if needed, the warning information is distributed to advanced users and cell phones, radio, television, sirens, and PA systems/fire alarm systems before the arrival of S-waves.

An earthquake warning system or earthquake alarm system is a system of accelerometers, seismometers, communication, computers, and alarms that is devised for rapidly notifying adjoining regions of a substantial earthquake once one begins. This is not the same as earthquake prediction, which is currently not capable of producing decisive event warnings.