California launches earthquake early warning app


(17 Oct 2019) FOR CLEAN VERSION SEE STORY NUMBER: apus125296

Earthquake early warning alerts will become publicly available throughout California for the first time this week, potentially giving people time to protect themselves from harm, state officials said Thursday.
The nation’s first statewide quake warning system will debut Thursday, coinciding with the 30th anniversary of the Loma Prieta earthquake that ravaged the San Francisco Bay area on Oct. 17, 1989, as well as the annual Great Shakeout safety drill.
Warnings produced by the ShakeAlert system will be pushed through two delivery systems: a cellphone app called MyShake and the same wireless notification system that issues Amber Alerts, meaning people may receive both notifications.
The state earthquake app, developed at the University of California, Berkeley, is available for download to IOS users through iTunes and through GooglePlay stores for Android phones.
The thresholds for an alert are an earthquake of magnitude 4.5 and shaking intensity level 3.
The ShakeAlert system is being developed by the U.S. Geological Survey and partners for the West Coast states. It is most complete in California.
The system does not predict earthquakes. Rather, it uses numerous seismic stations to detect the start of an earthquake and light-speed communications to send the data to computers that instantly calculate location, magnitude, intensity of shaking and create alerts to be distributed to areas that will be affected.
Depending on distance from the epicenter, the alerts may give warnings of several seconds to a minute before shaking arrives at a given location — enough time to duck under desks, pull a knife away from a surgical patient or shut down elevators, trains and industrial processes.
After lengthy testing, alerts were made broadly available to businesses, utilities, schools and other entities last year. The only large-scale public notification is in Los Angeles County, where an alerting app developed for the city of Los Angeles hasn’t been triggered yet.
The MyShake system maintains a database of which cellphones are in 10-kilometer-by-10-kilometer (6.2-mile-by-6.2-mile) cell grids and pushes the alerts to phones in zones where at least level 3 shaking will occur, so receiving an alert is not based on which tower the phone is communicating with, officials said.
The developers expect to improve the system through experience.
Most recently, the MyShake system was tested this week by a magnitude 4.5 quake in the San Francisco Bay Area and a 4.7 in central California. The median times from detection to alerts hitting phones was 2.1 seconds and 1.6 seconds, respectively, Allen said.
The Los Angeles app was criticized because it did not alert users when two powerful earthquakes struck an area of the Mojave Desert more than 100 miles north of the city on July 4 and 5.
Experts said the goal was to alert people who might experience potentially damaging shaking rather than simply feel some shaking. But the city later announced the threshold will be lowered to alert of “weak” shaking.

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