The warning system was developed by the California Office of Emergency Services, U.S. Geological Survey, UC Berkeley and Caltech.
On the 30th anniversary of the Loma Prieta Earthquake, California launched its statewide earthquake early warning system.
The system employs hundreds of sensors around the state that measure ground motion.
The sensors send instant signals to U.S. Geological Survey computers in Pasadena, which sends them to residents via the state's wireless emergency alert system.
