By Robert Sanders
While the United States takes baby steps toward a public West Coast earthquake early warning system, Mexico City has had such a system since the late 1980s. Citizens routinely download apps to their cellphones that alert them of impending shaking, and the apps even facilitate communication with rescuers for those pinned under debris. Some 12,000 speakers are mounted on poles throughout the city to broadcast warnings.
To determine how the public reacted to the early warning notices after the Sept. 7 Chiapas quake and the Sept. 19 Puebla quake, a team of seismologists from the University of California, Berkeley, the U.S. Geological Survey and the Earthquake Engineering Research Institute flew to Mexico City in September. Led by Richard Allen, director of the Berkeley Seismological Laboratory and a professor of earth and planetary science, the team hoped to come away with tips on how to make the U.S. system even better than those in Mexico and places like Japan.
In an editorial for the Dec. 1 issue of the journal Science, Allen and his colleagues highlight the lessons learned. Key among them are:
Even false alerts are valued: Despite fears that the public will lose faith in an early warning system that is not perfect and occasionally issues false alarms or alerts for quakes too distant to be felt, the team found that Mexicans “show a greater tolerance for alerts associated with little or no perceptible shaking than for late or missed alerts.” They even saw these alerts as an opportunity to practice protective actions and discuss earthquake safety.
“The public in Mexico recognizes the technical limitations of EEW (earthquake early warning) and is accepting of false alerts,” Allen said. “This means that the bar for a public system is perhaps quite a bit lower than folks in the U.S. had thought.”
“This should give us added confidence to accelerate deployment of EEW systems elsewhere,” the team wrote.
Simplicity: The prototype system for the U.S., ShakeAlert, is already deployed at dozens of businesses, utilities, fire departments and cities along the West Coast, and typically provides a countdown until shaking begins. The reconnaissance in Mexico emphasized the need to make the alert much simpler for the public: basically, just a prompt to take immediate action, which in the U.S. is “duck, cover and hold on.” More details can be provided after the shaking has subsided, the team concluded.
Consistency: All channels to the public should provide the same information. “Information from the public SASMEX system did not always align with information from the private SkyAlert system,” the team noted.
Create a seismic culture: To be effective, an EEW system must be coupled with proper and widespread training on how to take action, something that Mexico City has embraced. “This means closely pairing EEW development with disaster preparedness research, education, planning and policy,” they wrote.
“We learned some important lessons that should help speed the U.S. system towards its public roll out,” Allen said.
Co-authors on the editorial are Elizabeth Cochran of the U.S.G.S., Tom Huggins of Massey University, Scott Miles of the University of Washington and Diego Otegui of the University of Delaware.