A tsunami is a series of sea waves, usually caused by a displacement of the ocean floor by an undersea earthquake. As tsunamis enter shallow water near land, they increase in height and can cause great loss of life and property damage.

     Recent research suggests that tsunamis have struck the Oregon Coast on a regular basis. They can occur any time, day or night. Typical wave heights from tsunamis occurring in the Pacific Ocean, over the last 80 years, have been 20-45 feet at the shoreline. However, because of local conditions a few waves have been much higher-as much as 100 feet or more.

We distinguish between a tsunami caused by an undersea earthquake near the Oregon coast (LOCAL TSUNAMI) and an undersea earthquake far away from the coast (DISTANT TSUNAMI).

A LOCAL TSUNAMI can come onshore within 15 to 20 minutes after the earthquake-before there is time for an official warning from the national warning system. Ground-shaking from the earthquake may be the only warning you have. Evacuate quickly!

A DISTANT TSUNAMI will take four hours or more to come onshore. You will feel no earthquake, and the tsunami will generally be smaller than that from a local earthquake. Typically there is time for an official warning and evacuation to safety.

Evacuation for a distant tsunami will generally be indicated by a STEADY 3-MINUTE SIREN BLAST and an announcement over NOAA weather radio that the local area has been put into an official TSUNAMI WARNING. In isolated areas along beaches and bays you may not hear a warning siren. Here, A SUDDEN CHANGE OF SEA LEVEL should prompt you to move immediately inland to high ground. If you hear the 3-minute blast or see a sudden sea level change, first evacuate away from shoreline areas, then turn on your local broadcast media of NOAA weather radio for further information.