Earthquake Early Warning in the U.S.: ShakeAlert and the MyShake App
By Quake Tracker Live Editorial · Published November 9, 2026
ShakeAlert is the U.S. earthquake early warning system, operated by the U.S. Geological Survey with partner universities and state agencies. It detects an earthquake that has just begun and sends an alert to phones and other devices before the strongest shaking reaches you. You can receive it through the free MyShake app, through built-in Android Earthquake Alerts, or through Wireless Emergency Alerts on your phone. The warning is short, usually seconds to tens of seconds, but enough to Drop, Cover and Hold On.
What early warning is, and what it is not
Early warning is not earthquake prediction. Nobody can say that an earthquake will happen tomorrow or next week; our guide on whether earthquakes can be predicted explains why. ShakeAlert works only after an earthquake has started. It races the earthquake's own waves: the system sends its alert at the speed of data, while the damaging waves travel through the ground more slowly. The farther you are from the epicenter, the more time you gain. If you are very close, you may get an alert only as shaking begins, or after it has passed.
How ShakeAlert works
Earthquakes release two main kinds of waves. The first to arrive are P-waves, which are fast and usually cause weak shaking. The S-waves and surface waves that follow are slower but cause most of the damage. Seismic stations near the fault sense the P-waves within seconds and send the data to processing centers.
- Detection. Sensors close to the earthquake pick up the first waves. According to the Pacific Northwest Seismic Network, four or more stations must detect unusual shaking before the computers determine an earthquake's location and size.
- Calculation. The system estimates the magnitude and location in a few seconds and predicts how strongly the shaking will be felt in different places.
- Delivery. If the earthquake meets the thresholds, alerts are pushed out immediately to phones, apps and automated systems.
- Action. You, or an automated system, use the seconds. People drop, cover and hold on; trains can slow, elevators can open at the nearest floor and utilities can protect equipment.
The network behind it is big. In 2021, the PNSN reported more than 230 stations contributing in Washington, and press coverage cited about 155 in Oregon. The partners include the USGS, the Pacific Northwest Seismic Network at the University of Washington, a consortium of four West Coast universities (University of Washington, University of Oregon, UC Berkeley and Caltech) and state emergency agencies.
Where it is live: California, Oregon and Washington
Public alerts reached the West Coast in stages:
| State | Public alerts began | Notes |
|---|---|---|
| California | October 17, 2019 | First statewide public alerts, delivered through the UC Berkeley MyShake app and Wireless Emergency Alerts; run by the California Governor's Office of Emergency Services |
| Oregon | March 2021 | About 155 stations at launch |
| Washington | May 4, 2021 | Completed West Coast-wide coverage; more than 230 stations contributing at launch |
Sources: UC Berkeley, USGS, PNSN and press reports from the time of each launch. Station counts are from 2021 and the network has continued to grow.
If you live in one of these states, check recent shaking in California, Oregon or Washington to see how often moderate earthquakes happen. The system gives alerts for earthquakes of notable size, not for the many small ones recorded daily.
How to get alerts: MyShake, Android and WEA
There are three main channels. You can use more than one, and they are independent of each other.
- MyShake app. A free app from UC Berkeley for iPhone and Android, which also runs on Chromebook and macOS. Set the phone's location to "always on" so that nearby warnings reach you. MyShake also displays earthquake activity starting at magnitude 2.5, but its early warning alerts trigger only at 4.5 or higher.
- Android Earthquake Alerts. Built into many Android phones in California, Oregon and Washington, with no separate app. Keep location services enabled, since the system uses your general location to decide who gets an alert.
- Wireless Emergency Alerts (WEA). Text-style messages sent to WEA-capable phones, in the "Imminent Threat" category. These are reserved for larger earthquakes, magnitude 5 and above.
Alert thresholds
Alerts are tied to both the size of the earthquake and the shaking you are expected to feel. MyShake and Android alerts go out for earthquakes of about magnitude 4.5 and higher where you are expected to feel at least weak shaking (Modified Mercalli Intensity III). WEA messages are sent for magnitude 5.0 and higher, for people expected to feel light shaking (intensity IV) or more.
View the data
| Minimum magnitude | Value |
|---|---|
| MyShake: shows earthquakes from | M2.5 |
| MyShake & Android: alerts from | M4.5 |
| Wireless Emergency Alerts: from | M5.0 |
Sources: Cal OES, Pacific Northwest Seismic Network. The magnitude scale is logarithmic: an earthquake of magnitude 4.5 releases about 1,000 times more energy than one of magnitude 2.5, and one of 5.0 about 5.6 times more than one of 4.5. Intensity thresholds also apply (III for MyShake and Android, IV for WEA).
These thresholds explain why you may feel an earthquake and receive nothing: if it was small, or if the expected shaking at your location was below the cutoff, no alert is sent. That is by design, so that alerts keep their meaning.
How much warning will you get?
The honest answer is: it depends on where the earthquake starts. The Pacific Northwest Seismic Network gives these typical ranges for its region:
| Type of earthquake | Typical warning | Why |
|---|---|---|
| Shallow crustal earthquake | Fewer than 10 seconds | Often close to cities, so there is little distance for the alert to gain on the waves |
| Deeper intraslab earthquake | Up to about 10 seconds | Originates within the descending plate, farther below the surface |
| Cascadia Subduction Zone, rupture starts in Southern Oregon | 50 to 80 seconds for the Pacific Northwest | The rupture begins far away, so the alert has a long head start |
| Cascadia Subduction Zone, rupture starts near you | A few seconds | The waves are already close |
Source: Pacific Northwest Seismic Network. In most cases, warning time is seconds to tens of seconds.
What to do when an alert arrives
The message on your phone will usually say that an earthquake was detected and tell you to Drop, Cover and Hold On. Act immediately, without trying to look at the details.
- Drop to your hands and knees, cover your head and neck under a sturdy table or desk, or against an interior wall, and hold on until the shaking stops.
- If you are in bed, stay there and protect your head with a pillow.
- If you are driving, slow down, pull over somewhere clear of bridges and overpasses, and stay in the vehicle.
- Near the coast, once the shaking stops, move to high ground if it was strong or long. See our guide on tsunamis.
The full steps for different places are in our guide on what to do during an earthquake.
Limits of the system
- Blind zone. Close to the epicenter, shaking can arrive before or together with the alert.
- Late or missing alerts. California officials note that sometimes you get an alert only after you feel shaking, or after it has passed.
- Magnitude can change. The first estimate is made within seconds and can be revised. An early estimate near a threshold can lead to an alert for an earthquake that ends up slightly smaller, or to none for one that ends up larger.
- Coverage. Public alerts described here apply to California, Oregon and Washington, and you need a phone with location services on.
Accuracy has been good in practice. A 2024 study in the Bulletin of the Seismological Society of America reported that between October 17, 2019 and September 1, 2023, ShakeAlert created 95 events with a maximum magnitude estimate of 4.5 or higher, and 94 of the 95 were real earthquakes.
View the data
| Number of events | Value |
|---|---|
| Real earthquakes | 94 |
| False events | 1 |
Source: Lux et al., Bulletin of the Seismological Society of America, 2024 (Status and Performance of the ShakeAlert Earthquake Early Warning System). Counts events with a maximum magnitude estimate of 4.5 or greater between 17 October 2019 and 1 September 2023.
How this site fits in
Quake Tracker Live shows earthquakes that have already happened, from public seismic networks, and is not an official alert system. Use it to see what just occurred on earthquakes today or the biggest recent earthquakes, and rely on ShakeAlert, your local emergency officials and official channels for warnings.
Frequently asked questions
What is ShakeAlert?
ShakeAlert is the U.S. earthquake early warning system run by the USGS with university and state partners. It detects earthquakes that have started and sends alerts to phones and other systems seconds before strong shaking arrives.
Is the MyShake app free?
Yes. MyShake is a free app from UC Berkeley, available on the Apple App Store and Google Play. Set location to "always on" so you receive alerts for earthquakes near you.
How many seconds of warning will I get?
Usually seconds to tens of seconds, depending on how far you are from the epicenter. Close to a shallow earthquake it can be under 10 seconds; for a distant rupture it can be much longer.
Why did I feel an earthquake but get no alert?
Alerts are sent only for earthquakes of about magnitude 4.5 or larger where you are expected to feel at least weak shaking. Small earthquakes, or ones that did not meet the thresholds at your location, do not trigger alerts.
Which states have ShakeAlert alerts?
Public ShakeAlert alerts began in California in October 2019, Oregon in March 2021 and Washington in May 2021, completing West Coast-wide coverage.
Sources and further reading
- Pacific Northwest Seismic Network: ShakeAlert rolling out in Washington
- California Earthquake Early Warning: How to get warnings
- UC Berkeley: California rolls out first statewide early warning system
- Lux et al. (2024): Status and Performance of the ShakeAlert Earthquake Early Warning System
This guide is general information, not professional or emergency advice. Quake Tracker Live is not an official warning system; follow instructions from local authorities.