What's a Tsunami?

A tsunami is a series of waves generated by a large undersea earthquake or volcanic eruption. A tsunami can also be caused by an underwater landslide. Because tsunamis travel extremely fast in the deep ocean, a tsunami from hundreds or thousands of miles away can reach the San Francisco Bay shoreline in a matter of hours.

When a tsunami arrives, the first wave is almost never the biggest or worst. Tsunami surges can last for many hours, carrying damaging debris and leaving areas flooded. 

What to do before a Tsunami Hits 

In the event a Tsunami Warning is issued by Federal, State, or local authorities:

• Go to high ground or inland! Keep going until you are out of the Tsunami Hazard Zone.
• Stay there! Wait for the "all clear" from a reliable source. Tsunami waves may arrive for hours.

Do the same if any of the following natural signs occur:

• You experience a major earthquake. 
• Water suddenly recedes far from the shore.
• You hear a loud roaring sound from the ocean or Bay.

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