Earthquake early warning is the rapid detection of earthquakes, real-time assessment of the shaking hazard, and notification of people prior to shaking. Warning times range from a few seconds to a few minutes depending on your location and how big the earthquake is. The further you are away from the epicenter, the more warning time. The bigger the earthquake, the stronger the shaking at greater distances. An early warning should tell you how strong the shaking will be at your location, and how long until that shaking starts (the warning time).
A warning in your pocket: Dramatization of how early warning can be received and used.
The app is real, the children are real.
Who can benefit from earthquake early warning?
As an individual you can use a few seconds to move to a safe location: under a sturdy table, away from falling hazards like bookcases, ceiling lights and fixtures. In the 1989 Loma Pieta earthquake more than 50% of injuries were linked to falls. In the 1994 Northridge earthquake more than 50% of injuries were due to non-structural (falling) hazards. The total estimated cost of just injuries in the not-so-large Northridge earthquake is $2-3 billion. If everyone took cover before shaking, those losses could be halved.
Corporations, institutions and agencies can not only protect their personnel, they can also use automated control systems to further reduce injuries and damage: slowing and stopping trains, isolating hazardous chemical and machinery, starting emergency generators, moving data to safe storage, etc. Surgeons can lift the scalpel out of a patient, or off your eyeball. The metro/commuter rail system in the San Francisco Bay Area (BART) already uses alerts from ShakeAlert to automatically slow train when an earthquake occurs.
Public earthquake early warning systems already exist in Japan and Mexico City. Systems are also issuing alerts in Turkey, Taiwan, China and Romania. Testing is underway in many other parts of the world.
For more uses of early warning see
"Costs and benefits of earthquake early warning" by Strauss and Allen, Seismological Research Letters, 2016:
Support for the earthquake early warning efforts at UC Berkeley is provided by: