The Northern California Coast is the most tsunami-prone area of the continental United States

What Every Northern Californian Should Know About Tsunamis

  • Damaging tsunamis are not as rare as you might think. In the past 70 years:
  • 34 tsunamis have been recorded on the North Coast. Five caused damage

Tsunami Facts

  • Tsunamis may look like sloping mountains of water or a river in flood, usually choked with debris.
  • A tsunami always consists of many waves or surges spaced minutes to more than an hour apart.
  • The first surge is not the largest. The most damaging surges may arrive hours after the first and hazardous waves may arrive for twelve hours or longer.
  • Tsunamis are not surfable. If you’re a surfer, you know how little control you have if your board is in whitewater. A tsunami has no face, so there’s nothing for a surfboard to grip. The water isn’t clean, but filled with everything dredged up from the sea floor and the land the wave runs over including garbage, parking meters, pieces of buildings, and dead animals. You can’t dive beneath the wave because the entire water column is in motion, not just the top few feet. You can’t exit the wave either, because the trough behind may be 100 or more miles away, and all that water is moving towards you. Big-wave riders should save their talents—and their lives—for big waves that are generated by massive storms.

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Top-left Clockwise 1946-Hawaii The tsunami surge approaching Coconut Island in Hilo, Hawaii looked like a sloping mountain of water. 2004-Thailand When the water rushed in, it looked like a river in flood. 2004-Thailand In Phuket, the tsunami began as a withdrawal of the ocean water that exposed hundreds of feet of the sea floor. 2004-Indonesia In Banda Aceh the water was choked with debris.

How Will I Know if a Tsunami is Coming and What Should I Do?

Natural Tsunami Warnings | Draw down and Zone signs

NATURAL WARNING

  • Ground shaking that lasts a long time
  • A loud ocean roar
  • The water receding unusually far, exposing the sea floor

If you observe any of these warning signs, immediately go to higher ground or inland. A tsunami may arrive within minutes and may last for eight hours or longer. Stay away from coastal areas until officials permit you to return.

Natural and official warnings are equally important. Respond to whichever you hear or observe first.

Official Tsunami Warnings

OFFICIAL WARNING

Tsunami Warnings are announced via radio, television, telephone, text message, door-to-door contact by emergency responders,NOAA weather radios, or in some cases by outdoor sirens and announcements from airplanes.

When a tsunami warning is issued, move away from the beach. Seek more information without using your telephone. Use radio, television or the web and follow the directions of emergency personnel who may request you to evacuate beaches and low-lying coastal areas.