Earthquakes in California can't be predicted, but the state has two kinds of official earthquake information. Early warnings can reach some people seconds before strong shaking. Reports describe a quake after it has happened. They come from different systems and do different jobs, and it helps to have both set up.
How likely a big quake is
USGS's long-term forecast for California (UCERF3) puts the chance of one or more magnitude 6.7 or larger earthquakes somewhere in the state over 30 years at greater than 99% (USGS fact sheet). For the Los Angeles region the 30-year chance of M6.7+ is about 60%, and for the San Francisco Bay Area about 72% (USGS). These are long-range odds, not forecasts for any particular week.
Before shaking: ShakeAlert early warning
ShakeAlert is the earthquake early warning system for California, Oregon and Washington. USGS operates it with university and state partners. It detects an earthquake that has already started, estimates its size and the shaking expected in different places, and hands that to delivery partners. Alerts can arrive a few seconds before strong shaking. Very close to the epicenter, shaking may arrive before any alert can.
In California, the state's Earthquake Warning California program, run by Cal OES, delivers ShakeAlert-powered alerts through several channels. Each has its own thresholds (ShakeAlert):
| Channel | Sent for | Shaking expected where you are |
|---|---|---|
| Wireless Emergency Alerts | Magnitude 5.0 and up | Light (MMI IV) or stronger |
| MyShake app | Magnitude 4.5 and up | Weak (MMI III) or stronger |
| Android built-in alerts | Magnitude 4.5 and up | Weak (MMI III) or stronger |
| iPhone built-in alerts | Magnitude 4.5 and up | Weak (MMI III) or stronger |
MyShake, from the UC Berkeley Seismology Lab, is free on iPhone and Android. On iPhone, Apple's built-in Earthquake Alerts are part of Enhanced Safety Alerts in iOS 26. They are on by default and can be found under Settings, Notifications, Enhanced Safety Alerts (Apple). Wireless Emergency Alerts need no setup, as long as emergency alerts are on.
When an alert arrives, or you feel shaking first, the advice from the Earthquake Country Alliance is to drop, cover and hold on. Don't run outside or stand in a doorway.
After shaking: USGS reports
USGS, working with Caltech and UC Berkeley's seismic networks, publishes each earthquake's magnitude, location, depth and time. The first numbers are automatic estimates and may be revised as seismologists review the data. For bigger quakes, USGS adds a ShakeMap of estimated shaking and a Did You Feel It? map built from public reports. You can add your own report.
These reports are records of what happened, not warnings. For why the number in a report doesn't always match what you felt, see magnitude vs. intensity.
Tsunami alerts on the coast
A large offshore earthquake can trigger a tsunami alert for the California coast. These come from NOAA's tsunami warning system, with current messages at tsunami.gov, and warnings can reach phones through Wireless Emergency Alerts. If you're on the coast and feel strong or long shaking, move to higher ground or inland without waiting for an alert, and follow local officials.
Where Herebeat fits
Herebeat shows recorded earthquakes from USGS for the places you save, with magnitude, location, time and distance from your place, next to NWS alerts on the same map. You can choose which quakes notify you. It doesn't provide early warning, so keep Wireless Emergency Alerts on and use MyShake or your phone's built-in earthquake alerts for that.
Practise once a year
The Great ShakeOut drill is held on the third Thursday of October. This year that's 15 October 2026 (ShakeOut). It's a good moment to practise drop, cover and hold on, secure heavy furniture, and check that the alerts on your phone are switched on.
Sources
- USGS: Earthquake early warning overview usgs.gov
- ShakeAlert: Alert delivery thresholds shakealert.org
- Cal OES: California Earthquake Early Warning Program caloes.ca.gov
- Earthquake Warning California: Get alerts earthquake.ca.gov
- Apple: Emergency and government alerts on iPhone support.apple.com
- USGS: Latest earthquakes earthquake.usgs.gov
- USGS: Did You Feel It? earthquake.usgs.gov
- USGS: ShakeMap earthquake.usgs.gov
- NOAA: Tsunami.gov tsunami.gov
- USGS Fact Sheet 2015-3009: UCERF3 (California earthquake forecast) pubs.usgs.gov
- USGS FAQ: Earthquake probabilities for Los Angeles and the San Francisco Bay Area usgs.gov
- Great ShakeOut: FAQ shakeout.org
- Earthquake Country Alliance: Drop, Cover, and Hold On earthquakecountry.org
Checked on 3 October 2026. Agencies update their pages and products; the linked official page is always the reference. Spotted a mistake? Email info@herebeat.com.