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Island County > Emergency Management > Island County Tsumani Hazards


What is a Tsunami?

A tsunami is a series of high-energy waves radiating outward from a disturbance. Earthquakes may produce displacements of the sea floor that can set the overlying column of water into motion, initiating a tsunami. A tsunami can also be generated by a large landslide or from an underwater volcanic eruption. While many may think that a tsunami is a single large wave, it is often times several waves. These waves can sometimes be hours apart, but still caused by the same event.

Types of Tsunamis

There are two types of tsunamis:

Local Tsunami: A local tsunami provides minimal warning time for individuals to move to higher ground and evacuate. A tsunami generated from a significant Cascadia Subduction Zone earthquake would be considered a local tsunami for communities along the coastline and within parts of the Puget Sound.

Distant Tsunami: A distant Tsunami is caused by an event far away. These tsunamis may travel for hours across the ocean. The 2011 Tōhoku earthquake and tsunami would be a distant tsunami to the United States. This tsunami traveled across the Pacific Ocean and was detected in Alaska and Hawaii.

Tsunami Safety

In the event of a tsunami predicted to affect Island County, a Tsunami warning will be issued through the Emergency Alert System (EAS). The EAS is the nation’s public warning system and will be broadcast through cable television, radio stations, and mobile devices such as cell phones.

In the event of a tsunami warning…

  • Get away from the shoreline, move to higher ground and move as far inland as possible.
  • Evacuate as soon as you suspect or notice signs of an impending tsunami (draining of shoreline waters that are not tide related).
  • If you are in a boat, head out to sea.

Tsunami wave simulation for Washington State

Tsunamis in Washington: The Earth Science Lecture Series 



Ghost Forests of the Pacific Northwest - Evidence for Cascadia's Past Earthquakes