Tsunami General Information
Large, often very devastating waves are called tsunamis (or tidal
waves), can strike the Oregon Coast at any time. The giant
waves are caused by undersea earthquakes. They can occur along
the Cascadia Subduction Zone (see photos) - one of the largest
faults in North America. This fault line is about 32 to 70 miles
offshore and parallels the west coast. The cities of Coos Bay, North Bend and Charleston, Oregon sound a test Tsunami alert every Wednesday at 12 noon. The sirens really need to be upgraded and made much louder. I live about 1/2 mile from the fire department's warning siren in Charleston and I cannot hear the weekly test. It doesn't evoke much confidence in the system!
These "tidal waves" are very destructive and dangerous. They have struck the Oregon coast many times and will no doubtly strike again in the future. The tsunamis often follow within minutes after an underwater earthquake. Their speed is very quick, but they rapidly run out of water as the reach inland and begin to move uphill. Flooding can occur up to several miles inland along rivers and streams. Most tsunamis are not a single giant wave but rather many large waves which strike the coast over the course of several hours.
What can you do to Escape:
After notice than an earthquake has taken place move inland and uphill immediately.
Do NOT return to the shoreline after the first wave because many more may arrive for several hours.
The authorities will advise you when it is safe to return to your home and the shorelines.
Additional information may be obtained from the local emergency planning office or the Oregon Department of Geology and Mineral Industries.
Photo One: This is a cross section of the Juan de Fuca Plate. It is moving away from the ridge and is being forced under the overriding North American Plate. This process is called "Subduction".
Photo Two: Right hand Picture - This represents where the Cascadia Subduction Zone Lays and the different fracture zones in the Pacific Ocean.