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Coastal Hazards
Tsunami Hazard Maps for the Oregon Coast and Community Evacuation Brochures
Tsunami evacuation brochures for selected coastal communities

Tsunami Inundation Map (TIM) series maps
Tsunami hazard maps (official maps for implementation of ORS 455.446 and 455.447) by city/area north to south
TsunamiReady, TsunamiPrepared Program
Learn more at OregonTsunami.org

Tsunamis Hazard Maps Background
This information is from DOGAMI Open File Report 95-67
The tsunami hazard maps were produced to help implement Senate Bill 379 (SB 379), which was passed by the 1995 regular session of the Oregon Legislature.

SB 379, implemented as Oregon Revised Statutes (ORS) 455.446 and 455.447, limits construction of new essential facilities and special occupancy structures in tsunami flooding zones. The focus of the maps is therefore on implementation of this public safety bill and not on land use or emergency planning.

Tsunamis are caused by any large-scale disturbance of the sea floor. In nature these disturbances are generally caused by faulting, landslides, or volcanic eruptions. This project addresses only the most common cause, the simultaneous uplift and subsidence of the sea floor accompanying undersea earthquakes on large fault zones termed “subduction zones”. The shape of the deformed sea floor after an earthquake is transmitted to the overlying sea surface, forming the initial tsunami wave. Waves so generated can arrive at nearby coastlines in minutes, causing extensive damage and loss of life.

These subduction zone earthquakes also typically cause landslides which can greatly amplify the tsunami run-up should they occur under the sea or slide from land into water. This latter hazard is not directly addressed here but could be an important consideration when adding factors of safety for evacuation planning.

Scientific findings of the last several years have shown that the Oregon coast is vulnerable to great (Magnitude 8-9) earthquakes
that can occur on the offshore Cascadia subduction zone fault system .

The estimated chance in the next 50 years of a great subduction zone earthquake is between 10 and 20 percent, assuming that the recurrence is on the order of 400 ± 200 years and that the last one occurred about 300 years ago.