Earthquakes in California: why it matters, and how to get alerts

Earthquakes can happen anywhere in California. This section covers why prep matters, regional risks on the coast, in fire country, and in remote areas, and how to set up ShakeAlert, MyShake, and your county alerts.

Why this matters in California

California sits on a network of active faults, not just the famous San Andreas. The Hayward Fault in the Bay Area, the San Jacinto Fault in Southern California, and many other faults can also produce damaging shaking. Cal OES's MyHazards tool puts it plainly: earthquakes can occur everywhere in the state, so every California household has some earthquake risk, even if you do not live next to a well-known fault line.

A damaging quake can strike without a forecast. The 1994 Northridge earthquake is one statewide reminder of what falling household items can do: Earthquake Country Alliance points to a UCLA study of that quake in which about 55% of injuries were caused by falling furniture or objects, and only about 1% by building damage. Utilities may be out for days, roads can close, and 9-1-1 may be overwhelmed. Official guidance is to be ready to take care of your household for at least three days, and in California to aim for up to two weeks. If you live in a desert, mountain, or other remote area, plan on an even longer wait for outside help.

Start with a few free steps today: look up the hazards at your address on the Cal OES MyHazards map, sign up for your county's emergency alerts, and practice Drop, Cover, and Hold On with your kids. The Great ShakeOut drill is held each year on October 15, and it is a good date to run that practice at home.

Regional risks across the state

If you live on or visit the coast

Tsunamis can affect any part of the California coast. Look up your address, workplace, and favorite beach on MyHazards, and review California tsunami hazard maps or TsunamiZone.org so you know whether you are in a tsunami hazard zone and how to get to high ground. Cal OES and the California Geological Survey say that if you are in a tsunami hazard zone and you feel about 20 seconds or more of very strong shaking, move inland or to high ground as soon as you can do that safely, and do not wait for an official warning. If you are on a beach or in a harbor, move inland or to high ground after any earthquake. If maps or signs are not available, official guidance is to go about 100 feet above sea level or two miles inland. Stay there until officials say it is safe; waves can keep arriving for hours. If you are not in a tsunami hazard zone, you are safer staying put after the shaking stops.

If you also live with wildfire risk

Many California addresses have both earthquake and wildfire hazards. MyHazards maps fire hazard zones alongside earthquake risk. After a quake, fire is already a common problem because of gas leaks, damaged wiring, and weakened chimneys. In fire country, a quake can also damage the roads, water, and communications you would need if a wildfire starts later. Keep a go-bag ready for either event, know more than one way out, and follow CAL FIRE guidance on defensible space if you live in a fire hazard zone.

If you live in a rural, mountain, or desert area

Help and supplies may take longer to reach you, and roads can close because of landslides, snow, or damage. Earthquake Country Alliance, in statewide guidance developed with Cal OES, recommends at least 1 gallon of water per person or pet per day for at least three days and ideally two weeks, and says to store even more if you live in a desert or remote area. That same guidance asks families to think about what they would need to shelter at home for up to three weeks. Build your water, food, and medication supplies toward that longer window, and keep a paper map and extra warmth in the kit if you live in the mountains.

Set up ShakeAlert and MyShake

ShakeAlert is the U.S. Geological Survey early warning system for California, Oregon, and Washington. It does not predict earthquakes. Sensors detect a quake that has already started and can send a short warning before strong shaking reaches you. In California, the official public app is MyShake, from UC Berkeley in partnership with USGS and the California Governor's Office of Emergency Services (Cal OES). Many Android phones also have earthquake alerts built into the phone itself, and Wireless Emergency Alerts can arrive without an app if that setting is turned on.

What you need

• A smartphone and a few minutes
• The free MyShake app, from the Apple App Store or Google Play
• Your home address, so you can set HomeBase

Steps

1. Download MyShake

   Get it from the official Apple or Google store. It is free. Official setup guidance is at earthquake.ca.gov/get-alerts and myshake.berkeley.edu.

2. Allow notifications, and Critical Alerts on iPhone

   On first launch, allow notifications. On iPhone, also allow Critical Alerts so a warning can come through Focus or Do Not Disturb. On Android, add MyShake to your Do Not Disturb exceptions.

3. Set HomeBase to your home address

   MyShake can warn you about a quake that would affect your home even if you are not there, so you can check on kids or anyone who might be home. The app says this address stays on your device.

4. Set location access to Always

   That way you can also get alerts for wherever you are in the ShakeAlert region, not only at home. Official guidance from Earthquake Warning California is to leave location on so warnings can reach phones in the affected area.

5. Know what the alert means

   MyShake is built to warn for earthquakes around magnitude 4.5 and larger that may cause shaking at your HomeBase or current location. If the alert sounds, or you feel shaking, protect yourself immediately. Do not stand there reading the screen.

6. Check Android and Wireless Emergency Alerts too

   Android Earthquake Alerts are built into many Android phones in California. Also confirm Wireless Emergency Alerts are turned on in your phone settings. These are extra layers, not a reason to skip MyShake.