Wireless Emergency Alert system

ShakeAlert® and the Wireless Emergency Alert (WEA) system – FAQ 

Since October 2019, the USGS, the State of California, and other partners are testing public alert deliveries, powered by the ShakeAlert® Earthquake Early Warning system, to wireless devices via FEMA’s Wireless Emergency Alert (WEA) system and cell phone Apps. Currently, three Apps are in the testing phase, but publicly available: QuakeAlertUSA, MyShake, and an App developed by the City of Los Angeles. Testing of WEA and Apps in Oregon and Washington is expected sometime in 2021.

What is Wireless Emergency Alert (WEA)?

Wireless Emergency Alert (WEA) is a system that broadcasts public safety messages over the commercial cellular system. Customers with compatible smartphones, tablets or other mobile devices can receive geographically targeted, text-like messages alerting them to threats to safety in their area. Messages are sent by alert authorities through the Federal Emergency Management Agency’s (FEMA’s) Integrated Public Alert and Warning System (IPAWS), which validates messages before sending them to commercial mobile service providers for distribution to customers. IPAWS/WEA is used for all hazards including terrorist threats, severe weather, tsunamis, flash floods, AMBER alerts, and now, earthquakes.

What does a WEA alert look and sound like?

All WEA alerts, regardless of type, behave the same. The device makes a distinctive notification sound and the message pops up in a text window on the screen. Some devices with text-to-voice capability may read out the message text. WEA supports English and Spanish language messages. Users may opt-out of receiving WEA messages.

Why is the Wireless Emergency Alert (WEA) System being used for Earthquake Early Warning?

The USGS is committed to the delivery of ShakeAlert-powered public earthquake alerts through all available means. The WEA system plays a key role in delivering alerts to the public because it can reach the cell phones of a large number of users. This is why WEA was built and why it is used to deliver National Weather Service warnings and AMBER Alerts. WEA uses cell broadcast technology, which scales to the large population of California residents (millions) that could be affected by a significant earthquake.

What is the current status of ShakeAlert-powered alert delivery by WEA?

The WEA system is now delivering alerts to people in California for earthquakes that fit a certain profile. Currently, the time required to deliver alerts by WEA is variable, from a few seconds to tens of seconds depending on your cellular provider, your cell phone, and other factors. You may not receive a WEA alert if you are outside the alerted area, there are reception issues, or you have opted out of receiving alerts. The USGS, FEMA, and wireless providers are working to improve the delivery of alerts every step of the way, from earthquake detection to when you get an alert.

What factors affect when I get an alert from WEA or any other source?

Some alert delivery methods are faster than others. No matter how you receive an alert (for example, on your phone or over a public address system) it might arrive before, during, or after shaking reaches your location, depending on your distance from the quake and how you receive the alert. For every earthquake there is a zone near the epicenter where people will experience shaking before an alert can be delivered because of the time it takes to detect the earthquake, produce the alert and deliver it. Remember, no matter how the alert is delivered there will be people who will receive the alert during or after shaking arrives at their location. If you feel shaking that should be your prompt to take a protective action like Drop, Cover, and Hold On. Don’t wait for an alert.

What’s the difference between WEA and text messages?

A variety of technologies are used to send and receive text messages. These methods deliver messages to individuals and are inefficient for delivering a single message to many people. WEA is a different technology called cell broadcast that was designed by cellular companies for mass notification. It is optimized to send a single message to many people as quickly as possible without overwhelming the bandwidth of the cellular system.

What’s the difference between WEA and alert from smartphone Apps?

Smartphone Apps receive notifications using push-notification technology. This method has a large capacity but becomes less efficient as the number of recipients grows. Sending a burst of push-notifications to a large number of users may flood the cell data system causing messages to be delayed or lost. WEA is a different technology called cell broadcast that was designed by cellular companies for mass notification. It is optimized to send a single message to many people as quickly as possible without overwhelming the bandwidth of the cellular system. 

What can I expect from WEA now?

WEA alerts are currently being delivered to people who could feel light shaking or greater for earthquakes of magnitude 5.0 or greater. Initial tests of the WEA system by USGS and its partners have demonstrated that WEA delivery times can vary significantly depending on your carrier and the age and type of phone you have.  In some cases, WEA can be fast enough to deliver alerts to at least some people before they experience strong to severe shaking at significant distances (>40 miles) from the epicenter in large (magnitude 7+) earthquakes. For people near the epicenter alerts will usually arrive after the shaking has been felt or even after is has ceased.  This is particularly true for events in the magnitude 5-6 range, where strong shaking only occurs in a small area close to the epicenter.  Also, the magnitude estimates made in the first few seconds are not as accurate as the final estimates, so sometimes you will get an alert for an earthquake that is smaller than magnitude 5.0. You may not receive a WEA alert if you are outside the alerted area, there are reception issues, or you have opted out of receiving alerts.

What’s next for ShakeAlert use of WEA?

Use of WEA for distribution of ShakeAlerts in California is currently in test mode, to enable us to improve the performance of WEA alerting over time. Understanding the extent to which WEA can be a useful delivery mechanism for smaller earthquakes (especially those in the magnitude 5-6 range) is a topic of intense research and testing by the USGS and its university partners. The alerts that arrive after strong shaking has already occurred are part of this testing. The WEA system may become faster in the future and the criteria for delivering WEA alerts may change as the ShakeAlert system is improved. The ShakeAlert Earthquake Early Warning System is an important tool in our earthquake risk reduction toolbox, and it will improve over time.