Tsunami Preparedness in Santa Monica

A tsunami is a series of large waves generated by the sudden displacement of the ocean. Large earthquakes below or near the ocean floor are the most common cause, but landslides, volcanic activity, certain types of weather, and near earth objects (e.g., asteroids, comets) can also cause tsunamis. Most tsunamis are generated by earthquakes or landslides caused by earthquakes, and due to the unique terrain along the Santa Monica coast, residents must be prepared for these catastrophic events. Although the Santa Monica coast is great for recreational activities, tsunamis cannot and should not be surfed or swam. Tsunami waves are usually filled with life-threatening debris which can severely hurt someone, and the column of water does not have the same composition as a wind-driven wave.

If you are near the coast during a seismic event, a tsunami can be detected by strong ground shaking, a loud ocean roar, or the water receding unusually far and exposing the sea floor. A tsunami may arrive within minutes or hours later due to the proximity of the seismic activity. Tsunami waves can reach heights of 20 to 50 feet along the coast, but the first tsunami wave may not be the highest and a larger surge may occur hours after the first wave.

When a tsunami is detected, warnings will be issued by Wireless Emergency Alert, radio, television, telephone, text message, and door-to-door contact by emergency responders. By registering with the City of Santa Monica for SMAlerts, you will receive emergency updates via phone, email or text message to assist with evacuations within the City.

Learn more about preparing for other Santa Monica hazards here.

FAQ

Do I live in a tsunami hazard zone in LA County?

Portions of the Santa Monica coastline are within the tsunami inundation zone and will require an evacuation if a significant tsunami is detected. The City encourages each person who lives or works near the coast to find out if you are within the tsunami zone by searching the LA County Tsunami Hazard Area Map.

What is the difference between a tsunami warning, tsunami advisory and tsunami watch?

Tsunami Warning – A tsunami warning is issued when a tsunami with the potential to generate widespread inundation is imminent, expected, or occurring. Warnings alert the public that dangerous coastal flooding accompanied by powerful currents is possible and may continue for several hours after initial arrival. Warnings alert emergency management officials to take action for the entire tsunami hazard zone. Appropriate actions to be taken by local officials may include the evacuation of low-lying coastal areas, and the repositioning of ships to deep waters when there is time to safely do so. Warnings may be updated, adjusted geographically, downgraded, or canceled based on updated information and analysis.

Tsunami Advisory – A tsunami advisory is issued when a tsunami with the potential to generate strong currents or waves dangerous to those in or very near the water is imminent, expected, or occurring. The threat may continue for several hours after initial arrival, but significant inundation is not expected for areas under an advisory. Appropriate actions to be taken by local officials may include closing beaches, evacuating harbors and marinas, and the repositioning of ships to deep waters when there is time to safely do so. Advisories may be updated, adjusted geographically, upgraded to a warning, or cancelled based on updated information and analysis.

Tsunami Watch – A tsunami watch is issued when a tsunami may later impact the watch area. The watch may be upgraded to a warning or advisory or canceled based on updated information and analysis. Emergency management officials and the public should prepare to take action.

When should I evacuate?

Know if you live, work or play in a tsunami hazard zone. Visit the LA County Tsunami Hazard Area Map.

If you experience any of the natural tsunami signs below and are in a tsunami hazard zone, evacuate by foot/bicycle as soon as shaking stops.

Feel a strong earthquake with more than 20 seconds of strong ground shaking
See a sudden rise or fall of ocean levels
Hear a loud roar from the ocean

If you live outside of the tsunami hazard zone, wait for official instructions before evacuating.

If you hear that a tsunami warning or advisory has been issued, but did not feel an earthquake or get official notification, get more information. Listen to the radio, television or other information sources and follow the instructions of emergency personnel.

Will I be safe from a tsunami in a tall building?

Most buildings are not designed to withstand impacts from tsunami waves; therefore, members of the community are strongly urged to evacuate the hazard zone if a tsunami has been detected. If evacuation is not possible, the upper stories of some strong (e.g., reinforced concrete) and tall buildings can provide limited protection if no other options are available.

The height of the tsunami waves are equivalent to regular waves, why do we need to evacuate?

It is not safe to swim, surf, or boat during a tsunami. Although tsunami waves may be described as 1 to 3 feet in height, the force behind the tsunami wave presents the greatest danger. The additional force behind the tsunami wave can drive a 1 to 3 foot wave significantly farther inland than a wind-driven wave, creating large inundation zones with potentially life-threatening currents and debris.

Where can I find out more information about tsunamis?

A tsunami can strike any ocean coast at any time throughout the year. While they don't happen very often, they pose a major threat to coastal communities. Watch the National Weather Service Tsunami Preparedness video to learn more about tsunami warning signs and what to do.

More information about tsunami risk across the United States can be found at The Tsunami Zone website.