Simulated Earthquake Early Warning for M6.9 Loma Prieta, CA Earthquake

The Cell phone apps and BART alerts 12 seconds into the earthquake with an estimated magnitude of 6.0. The gray polygon denotes the first Cell phone alert zone, and the black polygon defines the BART alert zone (for MMI III+; the BART zone is for MMI IV+ so it is smaller), WEA alerts have not been received yet. All of the major cities that eventually experienced strong shaking would have received their first cell phone alert at about this time. Other symbols are the same as previous figure.