INFO PAGE
Tsunamis
A tsunami is a series of powerful ocean waves that can flood coastal areas, damage buildings, and create dangerous currents.
These waves are usually triggered by earthquakes, landslides, or other large disturbances in the ocean. Tsunamis can last for hours, and the first wave is often not the biggest—so it’s important to stay alert.
Tsunamis can also cause strong, unpredictable currents off beaches and in marinas and harbors, making it dangerous to be in those areas.
Tsunami Hazard Zone Map
Use our Tsunami Hazard Zone Map to find out what which areas are at risk of flooding if a tsunami were to affect San Francisco.
These zones (shaded in purple) show the areas that may need to be evacuated if a tsunami occurs because they have the highest risk of flooding.
Could a tsunami affect San Francisco?
Yes. San Francisco could experience three types of tsunamis, depending on where the earthquake or underwater disturbance happens:
Tsunami Type: Distance Source
Where it starts: 621 miles or more
Estimated Time to Reach San Francisco: 4 - 15 hours
Likelihood: Moderate
Tsunami Type: Regional Source
Where it starts: Less than 621 miles
Estimated Time to Reach San Francisco: 1 - 1.5 hours
Likelihood: Moderate
Tsunami Type: Near Source
Where it starts: 62 miles or less
Estimated Time to Reach San Francisco: 10-15 minutes
Likelihood: Low
How will you know if a tsunami is coming?
Official tsunami alerts
- Wireless Emergency Alerts (WEA): The National Weather Service (NWS) will send a loud, text-like alert to your phone if you are in an affected area. No sign-up is required.
- AlertSF: The San Francisco Department of Emergency Management (DEM) will send text alerts with safety instructions. Sign up at AlertSF.org or text your ZIP code to 888-777.
- Public Safety Vehicles: Emergency responders may drive through evacuation zones using lights and sirens (Code 3) and loudspeakers to issue warnings and evacuation orders.
- Broadcast Alerts: If time allows, officials may also use radio and TV alerts.
- National Tsunami Warning Center: Check for official updates from NOAA and the NWS.
Nature’s tsunami warnings
A tsunami can strike before official alerts are sent, especially if it's caused by a near-source earthquake. If you notice any of these signs, evacuate immediately:
- Strong shaking for 20 seconds or more, making it difficult to stand or walk.
- A sudden, loud ocean roar that sounds different from normal waves.
- The ocean quickly receding far from shore, exposing the seafloor.
If you experience any of these warnings, do not wait for an official alert. Move inland and to higher ground immediately.
The National Tsunami Warning Center (NTWC) issues different types of tsunami alerts
- Information Statement: No major threat. Stay aware.
- Tsunami Watch: A tsunami may be coming. Stay alert for updates.
- Tsunami Advisory: Strong currents are expected. Stay away from beaches and harbors.
- Tsunami Warning: Dangerous flooding is possible. Move to higher ground immediately.
Before a tsunami
- Make an emergency plan and gather supplies.
- Know the warning signs:
- Strong ground shaking for 20 seconds or more (making it difficult to stand or walk).
- A loud roaring sound from the ocean.
- Water suddenly receding far from the shore.
During a tsunami
- Know if you are in a tsunami hazard zone. Check the San Francisco Tsunami Hazard Zone Map to see if your home, workplace, or places you visit are in an area that may need to evacuate.
- If you feel strong shaking or see other warning signs, move inland and to higher ground immediately. Do not wait for an official alert—natural warnings mean a tsunami could arrive within minutes.
- If you are in a tsunami evacuation zone and receive a warning or order to evacuate, leave immediately. Evacuate on foot if you are able. Roads will become congested, and traffic can slow down or block first responders. Do not rely on a vehicle as part of your evacuation plan.
- Most buildings are not designed to withstand tsunami impacts. However, the upper stories of some strong (e.g., reinforced concrete) and tall buildings may be able to provide protection if no other options are available. Check with your building management if you are unsure whether the building you live or work in can withstand a tsunami impact.
- If there is time (for regional and distant-source tsunamis), officials will send out alerts with instructions. Follow evacuation orders and stay informed through AlertSF and Tsunami.gov.
Sign up for AlertSF to receive important updates before, during and after emergencies.
Text your ZIP Code to 888-777 or sign up at AlertSF.org.
Learn more
- Find out about how disasters and emergencies can affect San Francisco.
- Review the steps to get prepared for any emergency.
About
Brought to you by the San Francisco Department of Emergency Management (DEM). DEM manages San Francisco's everyday and not-so-everyday emergencies.
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