Tsunamis

Tsunamis

tsunami |(t)soōˈnämē|
noun ( pl. same or -mis ) a long high sea wave caused by an earthquake, submarine landslide, or other disturbance. ORIGIN late 19th cent.: from Japanese, from tsu ‘harbor’ + nami ‘wave.’

CLICK HERE TO VIEW THE TSUNAMI EVACUATION MAP

Tsunami are sometimes referred to as tidal waves. In recent years, this term has fallen out of favor, especially in the scientific community, because tsunami actually have nothing to do with tides. The once-popular term derives from their most common appearance, which is that of an extraordinarily high tidal bore. Tsunami and tides both produce waves of water that move inland, but in the case of tsunami the inland movement of water is much greater and lasts for a longer period, giving the impression of an incredibly high tide. Although the meanings of “tidal” include “resembling” or “having the form or character of the tides, and the term tsunami is no more accurate because tsunami are not limited to harbours, use of the term tidal wave is discouraged by geologists and oceanographers.

Tsunami Preparedness in Oregon

The principal generation mechanism (or cause) of a tsunami is the displacement of a substantial volume of water or perturbation of the sea. This displacement of water is usually attributed to either earthquakes, landslides, volcanic eruptions, or more rarely by meteorites and nuclear tests. The waves formed in this way are then sustained by gravity. Tides do not play any part in the generation of tsunamis.

Tsunami generated by seismicity

Tsunami can be generated when the sea floor abruptly deforms and vertically displaces the overlying water. Tectonic earthquakes are a particular kind of earthquake that are associated with the Earth’s crustal deformation; when these earthquakes occur beneath the sea, the water above the deformed area is displaced from its equilibrium position. More specifically, a tsunami can be generated when thrust faults associated with convergent or destructive plate boundaries move abruptly, resulting in water displacement, owing to the vertical component of movement involved. Movement on normal faults will also cause displacement of the seabed, but the size of the largest of such events is normally too small to give rise to a significant tsunami.

FLORENCE TSUNAMI WARNING SYSTEMS

For remote tsunamis generated far from the Oregon Coast:

1. EMERGENCY ALERT SYSTEM (EAS)

-KCST Radio 106.9 FM
-Network TV Channels

2. NOAA WEATHER RADIO

-Channel 162.500
-Lane County S.A.M.E Code: 041039

3. FLORENCE AREA SIREN TONES

Test: 60 sec. steady tone Last Friday of month at 11:00 a.m.
Warning: Wailing tone varying from high to low warble tone
EVACUATE IMMEDIATELY from beaches and inundation zone
All Clear: Westminster Chimes – Safe to return home

4. AUTOMATED TELEPHONE CALLS

To homes in inundation zone only

For tsunamis generated near the Oregon Coast

1. Dramatic Change in Sea Level at the Beach

Those residents in the inundation zone are to immediately Evacuate on Foot to high ground or to designated evacuation sites along Highway 101.

2. Violent Shaking from Cascadia Subduction Zone earthquake
If not in the inundation zone, Shelter-In-Place in undamaged home ONLY after all shaking stops and advised by authorities to do so.