California earthquake alerts: How to get notified before a quake strikes

After a 7.0 magnitude earthquake rattled areas near Humboldt County and prompted tsunami fears Wednesday morning, residents are being reminded again to not let these earthquakes "catch you off guard" by staying alert and in the know with earthquake warning systems.

California uses science, state-of-the-art ground motion monitoring, and new and existing alerting methods to deliver warnings to residents' cell phones before the strongest shaking arrives.

"Seconds to tens of seconds of alert can provide opportunity to take life-saving actions such as Drop, Cover, and Hold On and put devices into various forms of a safe mode," according to the state's Earthquake Warning California website.

How quickly someone gets the alert depends on how close they are to the origin of the earthquake. The closer someone is to the origin determines how quickly they will get the notification.

Officials said there are some instances where people might get the alert after the shaking has started or passed.

Types of Earthquake alerts

California uses the MyShake App, Android Earthquake Alerts, and Wireless Emergency Alerts to send warnings to residents.

Once you get the alert or feel shaking, that is your cue to drop, cover and hold on.

How they work

Wireless Emergency Alerts (WEAs): A system that is used nationwide that sends text-like messages to phones during emergencies or when there is an imminent threat to life. These types of alerts can be sent by state and local public safety officials, the National Weather Service, and the president.

WEA alerts are used in response to a 5.0 magnitude quake or greater and sent to people who will experience light shaking or greater.

MyShake app

MyShake App: The warning system sends a notification to cellphones that shaking is about to occur. The system uses ground-motion sensors to detect earthquakes that have already started and estimates their size, location, and impact. When it detects a significant magnitude, the system issues a ShakeAlert message, providing a warning before shaking begins.

MyShake alerts are used in response to 4.5 magnitude earthquakes or greater and sent to people who will experience a weak level of shaking or greater.

You can download the mobile app for free in the App Store and on Google Play.

Android alerts

Android Alert: Google partnered with the California Governor's Office of Emergency Services (Cal OES) and the United States Geological Survey (USGS) to send earthquake alerts directly to Android devices in California.

The early warning technology is automatically included in millions of Android users' phones.

Warnings delivered through the system are based on the ShakeAlert program, operated by Cal OES and the USGS, that analyzes data from seismic networks in the state, calculates preliminary magnitudes, and then estimates which areas will feel shaking.

Of note, the Android Alert system uses your phone's general location to determine who receives alerts, so it is important to enable location services.

Alerts are used in response to a 4.5 magnitude quake and sent to people who will experience a weak level of shaking or greater. 

For more information, Californians can click here.

KTVU's O. Gloria Okorie contributed to this report.