Richard Allen says that within "seconds of an earthquake’s first subtle motions, scientists can now predict with some certainty how strong and widespread the shaking will be." How this could save lives:

If an earthquake early-warning system had existed [for the 1989 Loma Prieta quake in the San Francisco area], it could have provided perhaps a 20-second warning to the heart of the region. This is enough time to slow and stop trains, issue “go around” commands to airplanes on final approach and turn street­lights redpreventing cars from entering hazardous structures such as bridges and tunnels. Workers in hazardous work environments could move to safe zones, and sensitive equipment could enter a hold mode, reducing damage and loss. Schoolchildren and office workers could get under desks before the shaking arrived. The region would be ready to ride out the violence to come.

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