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In years of a major achievement, the US Earthquake Warning System will now be able to issue alerts to cell phone users anywhere on the west coast of the continental states. -United from this morning.

At 8 a.m. on Tuesday, mobile users in Washington state finally had access to mobile alerts from the Earthquake Early Warning System. The alert system for mobile users was launched in Los Angeles at the end of 2018 and was extended to the rest of California at the end of 2019. In March, mobile phone users in Oregon began to have access to the alerts of the early warning system in the event of an earthquake.

The announcement means that anywhere from the Canadian border to the Mexican border, cell phone users are eligible to receive early alerts that could give a few seconds to perhaps more than a minute of warning that a distant earthquake is on its way. The system works because the speed of current communication systems is faster than the speed at which shaking waves travel through the ground.

“Now all three states will receive alerts on cell phones,” said Robert de Groot, earthquake specialist for the US Geological Survey and communications coordinator for its ShakeAlert early warning system.

Since smaller earthquakes are much more common than the most powerful and catastrophic earthquakes, if residents receive an alert, they will likely have a few seconds of warning before the tremors arrive from a quake. of distant land. This could be enough time for people to let go, cover themselves and hold each other, and automatic systems to send alerts to hospitals asking surgeons to remove patients’ scalpels; the elevators stop on the nearest floor; and trains begin to slow down, reducing the risk of derailment.

The earthquake early warning system could also give residents of the Pacific Northwest up to 80 seconds of alert before shaking due to a magnitude 9 earthquake along the area of subduction of Cascadia, a monstrous fault zone hundreds of miles off the west coast, stretching beneath the Pacific. Western ocean from Cape Mendocino in California west of Vancouver Island.

The Cascadia Subduction Zone last ruptured in such an earthquake on January 26, 1700 and sent catastrophic tsunamis not only to the Pacific Northwest, but thousands of miles into Japan .

The United States has developed an early warning system for earthquakes relatively late. Such systems have been in place for years in Japan, Taiwan and Mexico, with development usually starting or accelerating after catastrophic deaths from past earthquakes. The American system, however, gradually began to gain bipartisan political support without a deadly earthquake triggering action, with initial efforts being revived by a grant from the Palo-based Gordon and Betty Moore Foundation. Alto.

The reach of the Earthquake Early Warning System’s mobile alerts expanded last year with an update to Google’s Android mobile operating system. Google is now delivering early earthquake warnings direct to Android cell phones in California, Oregon, and with Tuesday’s announcement in Washington.

(Apple has not made a deal with the USGS to develop a similar system for iOS devices.)

Alerts can also come from the wireless emergency alert system, which sends SMS alerts similar to an amber alert alerting cell phone users to an abducted child. However, these wireless emergency alerts are generally considered slower than getting the alerts through an app.

In California and Oregon, smartphone users can also download free apps to receive early earthquake alerts. MyShake, developed by UC Berkeley, alerts users that an earthquake has been detected and tells them to take protective action. QuakeAlertUSA, developed by Santa Monica-based Early Warning Labs, offers additional tools: a countdown for when the tremors are expected to arrive, and also a note on how much tremors to expect, De Groot said.

The city of Los Angeles once had its own mobile app for the earthquake early warning system, ShakeAlertLA, which was the first such system. But it was pulled late last year, and city officials recommended people download the MyShake app.

It is possible to download more than one earthquake early warning app, De Groot said. “Receiving more than one alert is a good thing, because it serves as a sort of backup,” he said.

The earthquake early warning system was tested in Los Angeles County last September when a 4.5 magnitude earthquake hit the South El Monte area. QuakeAlertUSA gave De Groot, in west Los Angeles, a warning just as the shaking started at its location, and some users further away from the epicenter – in the western San Fernando Valley – have signaled a few seconds of notice before the shaking happened. An alert has been sent to 2.2 million Android devices, De Groot said.

At the end of 2019, the Earthquake Early Warning System sent its first public alert, warning more than 40 earthquake people – for a 4.3 magnitude earthquake in a remote mountainous region between the coast central and the valley of San Joaquin.

In order for the earthquake early warning system to send an alert to mobile phone applications in a particular area, the earthquake must be recorded as having a magnitude of at least 4.5 and it must produce “Weak tremors” – the type that is felt inside and can be felt. like a passing truck. It is known as a level 3 tremor on the Modified Mercalli Intensity Scale.

The magnitude of an earthquake and the predicted intensity of the tremors must be more powerful before an early earthquake alert can be sent through the Amber-type wireless emergency alert text messaging system Alert. These alerts can only be triggered for earthquakes of at least 5 magnitude and sent to areas prone to “light tremors”, felt by most people indoors, shake dishes, windows and more. doors, and cause creaking and crackling on the walls. like a heavy truck hitting the building. This is known as the Modified Mercalli Intensity Scale Level 4 tremor.

Officials revised the thresholds to trigger alerts for less powerful earthquakes and less intense tremors after many people in Los Angeles complained that the warning system had not issued a warning before. the 2019 Ridgecrest earthquakes, the largest of which was magnitude 7.1.

The USGS is still working on building the earthquake sensor system in rural areas of the West Coast that will eventually allow alerts to be issued even faster. About 70% of the seismic station network is complete, with full completion estimated at the end of 2025.

Managers are also working to improve the computer software system designed to quickly analyze incoming shakes. One flaw that became apparent after the magnitude 9 earthquake of 2011, which triggered a deadly tsunami in northeastern Japan, is that the earthquake detection system initially underestimated the final magnitude of the earthquake. earthquake.

“Right now the algorithms are working really well – up to magnitude 8. And that was the case in Japan,” De Groot said.

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