Tsunamis

What is tsunami?
A tsunami is a series of ocean waves that can cause dangerous coastal flooding and other damage. Tsunamis are usually caused by a severe earthquake or landslide that displaces a large amount of ocean water. Tsunami waves can last for many hours; the first wave is almost never the largest. Tsunamis can also cause strong, unpredictable currents off beaches and in marinas and harbors, making it dangerous to be in those areas.

The National Tsunami Warning Center (NTWC) issues four general types of tsunami bulletins:

Possible NTWC Tsunami Bulletins
NTWC Bulletin Type Meaning NTWC Suggested Local Response
Information Statement Minor waves at most None
Level of Danger Being Evaluated Danger not yet known; Watch or Advisory unlikley Stay alert for more information
Tsunami Watch Danger not yet known; Warning or Advisory likely Stay alert for more information
Tsunami Advisory Strong currents likely Stay away from the shore
Tsunami Warning Inundating (flooding) waves possible Full evacuation suggested

 

What types of tsunamis may San Francisco experience?
San Francisco may experience three types of tsunamis: distant source, regional source, and near source, based on where the earthquake or other source event occurred. For information on each type see the table below.

Types of Tsunamis San Francisco May Experience
Tsunami Types Source Event Distance from San Francisco Estimated Time to Reach San Francisco Likelihood of Occuring
Distance Source 621 miles or more 4 - 15 hours Moderate
Regional Source Less than 621 miles 1 - 1.5 hours Moderate
Near Source 62 miles or less 10-15 minutes Low

 

What are my tsunami risks?
Use this map to find out what your tsunami risks are in San Francisco. The map shows the following:

  • Tsunami Evacuation Zones: These zones show the areas that may need to be evacuated if a tsunami occurs.
  • Tsunami Evacuation Sites: Locations away from the evacuation zones where evacuated residents can assemble.


How can I prepare for a tsunami?
Know the warning signs: Strong ground shaking for 20 seconds or more (making it difficult to stand or walk), a loud ocean roar, or the water receding are all nature’s warnings. If you are by the water move inland and to higher ground immediately. If there is time (a distant source tsunami) we will send out alerts and instructions.

In a distant-source or regional tsunami, the City will send out alerts and instructions. The Outdoor Public Warning System sirens, Wireless Emergency Alerts (alerts on your mobile device), and the Emergency Alert System (alerts of television and radio) may also be used to alert residents and visitors of San Francisco about possible danger. If you hear the Outdoor Public Warning System sirens, tune your radio or television to local news channels for information and instructions.

AlertSF is another way the City will send alerts. Sign up by texting your zip code to 888-777 or by visiting www.alertsf.org

Prepare and plan ahead of time: Prepare yourself by gathering supplies, planning ahead, and getting connected with your community. 

  • Pack a go bag and store it somewhere quickly accessible. Your bag should have things like water, extra clothes, and first aid kit.For a list of what should be in your go bag, see: http://sf-fire.org/sites/default/files/FileCenter/Documents/3568-Go%20Bag.pdf
  • When you have to act fast, having a plan that you’ve practiced is the key. Start a plan by visiting www.sf72.org/plan.
  • Get to know your neighbors and look out for each other now. Find out who can help and who needs help in an emergency.
  • Get trained in how to take care of yourself after a disaster by taking the San Francisco Fire Department's FREE Neighborhood Emergency Response Training:  http://sf-fire.org/neighborhood-emergency-response-team-nert