Tsunamis
Unlike regular ocean tides, tsunamis are not caused by the tidal action of the moon and sun.
How Tsunamis Work
When the ocean floor suddenly shifts, it displaces a large volume of water. The most common cause of a tsunami is an underwater earthquake. This movement creates waves that spread outward in all directions.
Tsunamis travel long distances with very little loss of energy because of their long wavelength. In deep ocean water, they can move at speeds of up to 550 miles per hour, allowing them to cross entire oceans in less than a day.
In deep water, the waves may be barely noticeable, but as they approach land, they slow down and increase in height.
Why Tsunamis Matter + Warnings
Why Tsunamis Matter
Tsunamis can cause severe flooding, damage buildings and infrastructure, and put lives at risk. In California, coastal areas are especially vulnerable, and waves can arrive within minutes following a nearby earthquake.
Warnings
Tsunami warning centers monitor earthquakes and alert communities when there is a risk. In some cases, warnings may provide time to prepare and evacuate.
However, if an earthquake occurs near the coast, waves can arrive within minutes.
The earthquake itself may be the only warning.
What to do
- If you feel strong shaking near the coast, move to higher ground immediately
- Do not wait for an official warning
- Stay away from the shoreline until authorities say it is safe
Explore Tsunami Resources
Understanding Tsunami Risk in California
- California Department of Conservation – Tsunami information and hazard data
- California Governor’s Office of Emergency Services – Preparedness and response
- Tsunami Threat to California – research and risk findings