Update, 7:45 a.m. Thursday: The MyShake test alert you might have received on Thursday morning at 3:19 a.m. was a mixup between time zones in the test alert system, according to USGS. The real test alert is still scheduled for 10:19 a.m. Thursday.

Update, 12:00 p.m. Wednesday: The emergency alert you might have received on Wednesday morning at 9:30 a.m. was for a real 4.2 magnitude earthquake just east of the Bay Area city of Antioch, near Isleton in Sacramento County. The MyShake emergency alert test detailed below is unrelated and should still go ahead as scheduled on Thursday morning.

Wednesday morning’s earthquake was initially overestimated as having a 5.7 magnitude by ShakeAlert USGS, which triggered the WEAS emergency alert on our cellphones. Ultimately, the earthquake’s magnitude was downgraded to 4.2.

“Our goal is public safety. And so yes, there are going to be events that will be overestimated because every earthquake is a little different,” said Robert-Michael de Groot, coordinator at ShakeAlert Earthquake Early Warning System, USGS. “The most important point about the earthquake early warning system is public safety. We try to maximize public safety.”

De Groot said the fact that MyShake overestimated the magnitude of this quake is “the system doing what it does normally.”

Original story: Do you have the MyShake earthquake warning app downloaded on your cellphone?

Over 2 million Californians already do — and they’ll be getting a loud earthquake test alert on Thursday morning, as part of the Annual Great ShakeOut quake preparedness drill that takes place across the globe.

This alert is coming on the heels of a test of the FEMA emergency alert system that was sent to phones nationwide. Keep reading for what you need to know about this latest test alert — and more ways to get these earthquake warnings for real.

When will the MyShake earthquake test alert happen?

The MyShake app will be sending the test alert on Thursday, Oct. 19 at 10:19 a.m. PST.

Unlike that FEMA test alert that almost everyone experienced earlier this month, this phone alert will only apply to people with the MyShake app living in California, Oregon and Washington.

What will the alert look and sound like?

The MyShake test alert will be in the form of an image that will tell people to “Drop, Cover, and Hold On.” You’ll also get an audio alert that will signify that this is a test.[aside postID='science_1977213,science_1936949,science_1949019' label='Related coverage']

The MyShake app, developed by UC Berkeley seismologists and engineers as an early earthquake warning system, gets its quake data from the U.S. Geological Services (USGS) ShakeAlert system. The app processes that data, and then distributes the alerts to where they need to go, according to de Groot, the ShakeAlert coordinator.

“The USGS role is critical in terms of how MyShake operates,” de Groot said.

How can I get the MyShake app if I don’t already have it?

If you have an iPhone, you can download the MyShake app from the Apple app store.

If you have an Android phone, you can download MyShake from the Google Play store — but Android phones will also get these alerts automatically through the Android operating system (more on this below.)

Read more about the evolution of the MyShake app.

How will this system be used when a real earthquake is detected?

When an earthquake happens, multiple earthquake stations will detect the shaking of the ground. Algorithms then estimate the earthquake’s location and expected magnitude.

“If the earthquake is estimated to be magnitude 4.5 or greater, MyShake delivers an alert to phones in areas where shaking is predicted,” said Christina Valens, a data analyst at UC Berkeley Seismological Laboratory.

If someone is far enough from the earthquake’s epicenter, they will receive the alert a few seconds before the ground shaking gets more intense. These seconds of warning can be used to take protective action such as Drop, Cover, and Hold On, she said.

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I have the app, but what if I don’t get the test alert?

If you have the MyShake app, and you don’t get the alert on your phone on Thursday, don’t worry: It might be due to a few reasons.

Your alerts and notifications might be disabled for the MyShake app, or MyShake may not have permission to run in your phone’s background. Since the alert will be sent to phones in California, Oregon and Washington, the app will rely on your location data in order to send you the test alert.

Valen says if you have your location services turned off, you might not be able to receive the alert. Valen encourages people to contact MyShake support if they notice a problem on the app.

If my phone is off or on airplane mode, will I receive the alert?

Just like a normal alert, MyShake is unable to send test alerts to phones that are off or in airplane mode, according to Valens.

For people who have the MyShake app and prefer not to receive the alerts on Thursday, MyShake advises people to temporarily disable the app notifications from 10:00 a.m. to 11:00 a.m. on the day.

“Though we highly encourage everyone to participate in ShakeOut, MyShake is considering adding an opt-out feature for test alerts in the future,” Valen said.

Find more frequently asked questions about MyShake here.

What are other ways than MyShake to get an alert if a real earthquake hits?

USGS’s ShakeAlert Earthquake Early Warning System (EEW) sends earthquake alerts to people’s phones in multiple ways.

The Wireless Emergency Alerts (WEA), MyShake alerts, the QuakeAlertUSA app for California and Oregon and the ShakeReadySD app for San Diego residents are a few ShakeAlert-powered alerts that people can sign up to.[pullquote align="right" size="medium" citation="Christina Valens, data analyst at UC Berkeley Seismological Laboratory"]“It may feel a little silly waiting under a table while nothing happens, but ShakeOut is meant to be an opportunity to practice and build muscle memory for when we experience actual earthquakes”[/pullquote]

Since 2020, Android phones have also been capable of receiving earthquake early warning alerts through Google’s Android operating system — though users should still check their settings to make sure that earthquake alerts are enabled.

If an earthquake is expected to be magnitude 5 or greater, a Wireless Emergency Alert (WEA) will be sent to WEA-capable devices, Valens said.

MyShake differs from these other alert delivery tools in that it collects user experience reports for earthquakes greater than magnitude 3.5 and uses motion data captured by phones for research purposes, said Valen.

The hope for this test alert is that when people receive it, they Drop, Cover, and Hold On.

“It may feel a little silly waiting under a table while nothing happens, but ShakeOut is meant to be an opportunity to practice and build muscle memory for when we experience actual earthquakes,” Valen said.

“Also, ShakeOut is a great opportunity to make a disaster plan, build an emergency supplies kit, and identify potential hazards that could cause injury when an earthquake happens,” she said.

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