ShakeAlert Earthquake Early Warning: How Alerts Reach Your Phone
ShakeAlert is the earthquake early warning system managed by the U.S. Geological Survey (USGS) for California, Oregon and Washington. It detects an earthquake that has already started and sends alerts that can arrive seconds before strong shaking reaches some areas. It does not predict earthquakes. Phone alerts come through Wireless Emergency Alerts, the Android and iPhone operating systems and the MyShake app, each with its own thresholds.
USGS describes ShakeAlert as the nation’s only public earthquake early warning system. The USGS-managed ShakeAlert site says it serves over 50 million residents and visitors in the three states.
Where does ShakeAlert work?
USGS states that statewide public alerting began in California in October 2019, expanded to Oregon in March 2021 and to Washington in May 2021. A USGS phone-alert card dated February 2026 lists the service as available in Washington, Oregon and California.
As of November 2026, the official ShakeAlert site lists only these three states. USGS has published a Phase 1 technical implementation plan for expanding ShakeAlert to Alaska (Open-File Report 2025-1003). To see recent activity in the covered states, open recent earthquakes in California, recent earthquakes in Oregon or recent earthquakes in Washington.
How does ShakeAlert detect an earthquake?
USGS explains the sequence in a few steps. The P wave, the fastest seismic wave, trips sensors placed across the region. The data go to a ShakeAlert processing center, which estimates the location, the size and the expected shaking. If the earthquake fits the right profile, USGS issues a ShakeAlert message.
Licensed Alert Delivery Partners turn that message into alerts for people or into automatic actions, such as slowing trains or closing water valves. The warning works because the message travels almost instantly, while shaking waves move through the shallow Earth at speeds of one to a few kilometers per second.
Alerts are tied to expected shaking, measured on the Modified Mercalli Intensity scale. Our guide to magnitude vs intensity explains what “weak” (MMI III) and “light” (MMI IV) shaking mean.
How do ShakeAlert alerts reach phones?
A USGS card on earthquake early warning for cell phones, dated February 2026, lists four routes.
| Route | Who delivers it | Expected shaking at your location | Minimum magnitude |
|---|---|---|---|
| Wireless Emergency Alerts (WEA) | FEMA, to all WEA-capable cell phones | Light or greater (MMI IV+) | 5.0 |
| Android phones | The Android operating system | Weak or greater (MMI III+) | 4.5 |
| iPhone | The iOS operating system | Light or greater (MMI IV+) | 4.5 |
| MyShake app | The app (download required) | Weak or greater (MMI III+) | 4.5 |
USGS notes that there is no app called “ShakeAlert” to download. MyShake was developed by UC Berkeley, is sponsored by the California Governor’s Office of Emergency Services and is free in the Apple and Google app stores.
To check the settings on your phone:
- For WEA, USGS says the setting may be listed under Emergency Alerts or Government Alerts, depending on the phone.
- On an iPhone, Apple’s support page says Earthquake Alerts are part of Enhanced Safety Alerts, require iOS 26.2 or later and are on by default. The path is Settings, then Notifications, then Enhanced Safety Alerts under Enhanced Alerts, then Earthquake Alerts.
- On Android, Google provides ShakeAlert-powered alerts built into the operating system in California, Oregon and Washington.
- For MyShake, download the free app; USGS lists it among the cost-free options.
Apple says its Earthquake Alerts look and sound different from Government Alerts sent by local authorities. For other ways official alerts reach phones, see our guide on how to get emergency alerts.
How much warning can ShakeAlert give?
USGS describes the warning as seconds to tens of seconds. Delivery speed varies by route. USGS says it can be as short as a few seconds for apps like MyShake or significantly longer through WEA, and some users may not receive a WEA alert for a particular earthquake.
Near the epicenter, alerts can arrive late. USGS research describes a late-alert zone where damaging shaking can begin before the alert arrives. Its size depends on the earthquake, how dense the sensor network is and the delivery method, and one USGS report puts it at roughly 0 to 30 km (0 to 19 miles) from the epicenter. USGS says people should take protective action as soon as they feel shaking, whether or not an alert has arrived.
What can’t ShakeAlert do?
- Predict earthquakes. ShakeAlert detects an earthquake already in progress. The USGS early warning overview explains the difference.
- Alert for every earthquake. Phone alerts go out only when the magnitude and expected shaking meet each route’s thresholds, and partners use varied thresholds.
- Beat the shaking everywhere. People in the late-alert zone may feel shaking first.
- Get every estimate right at once. A USGS study of the 2019 Ridgecrest sequence, before statewide public alerting began, found that the system underestimated the magnitude of the M7.1 mainshock because of software and hardware issues.
The free USGS Earthquake Notification Service sends email or text notices about earthquakes, but USGS states that it is not an early warning system. Our guide on earthquake magnitude explains why early magnitude estimates are often revised.
What does USGS advise when an alert arrives?
USGS says that if you feel shaking or get an alert, immediately Drop, Cover and Hold On, or take another protective action. A USGS card dated December 2024 adds these points:
- Using a wheelchair or walker: Lock, Cover and Hold On.
- Driving: slow down, pull over and stop.
- On the coast: after the shaking stops, go to high ground or inland immediately. USGS says the shaking is your tsunami warning and that tsunami waves may arrive for hours. Stay there until local officials say it is safe to return.
The USGS page Be ShakeAlert Safe lists the current ways to receive alerts. Ready.gov has the federal guidance on what to do during and after an earthquake. Follow your local emergency officials.
Bottom line
ShakeAlert covers California, Oregon and Washington. It can give seconds to tens of seconds of warning, but not to everyone and not for every earthquake. Keep WEA turned on, check the Earthquake Alerts setting on your phone and act on the shaking itself if it arrives before the alert.
FAQ
Do I need to sign up for ShakeAlert?
No. USGS lists several cost-free routes. WEA reaches capable phones without signing up, Android and iPhone deliver alerts through their operating systems, and MyShake requires a download.
Why didn’t I get an alert when I felt an earthquake?
The earthquake may have been below the magnitude or shaking thresholds for your route, you may have been in the late-alert zone near the epicenter, or WEA delivery may have been slow or missed your phone. USGS notes that some users may not receive a WEA alert for a particular earthquake.
Does ShakeAlert work outside California, Oregon and Washington?
Not as of November 2026. USGS has published a planning report for expansion to Alaska.
Is ShakeAlert the same as the USGS earthquake email service?
No. The USGS Earthquake Notification Service sends notices after earthquakes and is not an early warning system.