Oregon Coastal Atlas - Tsunami Hazards

Tsunami Hazards

Animation of hypothetical Tsunami along the Pacific Northwest Coast modeled by USGS

Tsunamis rank as one of the most dangerous natural disasters that could affect the Oregon coast. Although not frequent in occurrence, the damage caused by these catastrophic events is immediate and life threatening. The most destructive type of tsunami would be generated locally by a Cascadia subduction zone earthquake of magnitude of 8.0 to 9.0, or greater. Devastating tsunamis waves would be expected to arrive along the Pacific Northwest coast including Oregon within 5 to 30 minutes after such an event, providing very little evacuation time.

Tsunami Preparation

Tsunami Evacuation sign

Could a natural disaster like the tsunami that hit the countries around the Indian Ocean happen here in Oregon? “In a word, yes,” says James Roddey, Community Education Coordinator with the Oregon Department of Geology and Mineral Industries (DOGAMI). “We have a similar active fault offshore, so we will someday experience an earthquake and tsunami similar to the one that just hit Southeast Asia. We can expect a magnitude 9 earthquake and resulting tsunami that would devastate the Pacific Northwest coast from Cape Mendocino to British Columbia. The bad news is that it would be a horrible event. The good news for Oregon and the Pacific Northwest is that we are much better prepared than the countries around the Indian Ocean to respond to an event like this.”

DOGAMI, Oregon Emergency Management (OEM) and many other state and local agencies, under a mandate from the Governor’s Office and the State Legislature, have been working for the last decade to prepare coastal communities for the possibility of a devastating tsunami.

Tsunami Innundation Mapping & Evacuation Planning

Tsunami Evacuation
PDF Maps
for Your Community

Beginning in 1995, tsunami inundation maps were produced for the whole coast to implement Oregon Senate Bill 379, which limits construction of critical and essential facilities in tsunami inundation zones. Working in close partnership with the National Oceanic and Atmospheric Administration (NOAA), OEM, Oregon Graduate Institute of Science and Technology (now part of OHSU), and local governments, DOGAMI has produced detailed tsunami inundation maps and evacuation route maps for most of the populated communities of the Oregon coast.

DOGAMI produces tsunami innundation zone maps, like this one for Gold Beach, to help coastal communities prepare and mitigate this dangerous natural hazard. The red areas indicate low lying areas most vulnerable to a tsunami.

DOGAMI is also working with OEM, Oregon Department of Transportation, and the Oregon Parks and Recreation Department to place tsunami information signs along the coast and at many state parks. Many communities have installed warning systems to alert people of an approaching tsunami and many coastal towns have installed tsunami evacuation route signs.

On a national level, NOAA has created a Pacific Ocean-based tsunami monitoring and warning system that can pinpoint where and when a tsunami might strike the coast from distant sources. These warnings are relayed to coastal communities throughout Oregon, the West Coast, Alaska, and Hawai’i. This is all part of an international effort to reduce the loss of life and property along the coastlines of the Pacific Rim.

Learn more at: http://www.tsunami.noaa.gov/

NOAA has also partnered with DOGAMI and OEM to develop an innovative tsunami hazard educational pilot program that is currently underway in Seaside. Cannon Beach, Manzanita, Nehelam and Wheeler have been named TsunamiReady communities by NOAA for the work they have done in preparation for a tsunami.

Learn more about Tsunami Ready communities at: http://www.tsunamiready.noaa.gov/

As much as has been done to prepare coastal communities in Oregon for tsunamis, there is still much more to do. A survey of coastal residents taken in 1998 showed that many people remain unclear on what causes tsunamis and what to do if they felt a large earthquake at the coast.

“We realize that our work is only partially finished when we release a tsunami hazard map. As much as we’ve done to get the word out, we have to continue to educate, inform and advise coastal residents and visitors that they have to be prepared,” says State Geologist Vikki McConnell. “Our warning systems need to work better and people at the coast really need to take the tsunami threat seriously. Their lives depend on knowing what to do when a large earthquake and tsunami occur at the coast.”

Learn more about tsunamis and the Oregon coast in the following DOGAMI Factsheet:
http://www.oregongeology.com/sub/publications/tsunami-factsheet_onscreen.pdf

Be Prepared!
Coastal residents and visitors should learn where the tsunami evacuation zones are for their communities. A local tsunami can reach the shore in minutes. The earthquake may be the only signal to move quickly inland and to high ground.
During a tsunami evacuation, do not linger or go to the beach to watch for the tsunami. An approaching tsunami travels at jet speeds in the open ocean and cannot be outrun when making landfall.

Information provided by the Department of Geology and Mineral Industries