Is the Cascadia fault off the western coast of North America?
At 9PM on January 26, 1700 one of the world’s largest earthquakes occurred along the west coast of North America. The Cascadia fault is the boundary between two of the Earth’s tectonic plates: the smaller offshore Juan de Fuca plate that is sliding under the much larger North American plate.
Is the Pacific Northwest ready for the next Cascadia EQ tsunami?
Geologists have also determined the Pacific Northwest is not prepared for such a colossal quake. The tsunami produced could reach heights of 80 to 100 feet (24 to 30 m). A 2004 study revealed the potential for relative mean sea level rise (caused by subsidence) along the Cascadia subduction zone.
What would happen if the Cascadia subduction zone rupture?
A Tsunami is Born When the Cascadia subduction zone ruptures, it causes part of the seafloor to move abruptly upwards. This displaces the column of water above the rupture, and the result is a tsunami: a series of waves that travel outwards in all directions from the place where the uplift occurred.
Will the Juan de Fuca plate disappear?
The North American plate is riding up over the portion of the Pacific Ocean seafloor to the west of the U.S., identified as the Juan de Fuca Plate. Eventually, the Juan de Fuca plate will disappear beneath the N. American plate and be consumed within the mantle that lies beneath the crust of the earth.
How far would a tsunami travel up the Columbia River?
Any water level increases caused by a tsunami would be so slight as to be almost immeasurable around the Portland metropolitan area or Bonneville Dam, the study showed. But water could rise as much as 13 feet just inside the mouth of the Columbia River, and almost 7 feet within a few miles of Astoria.
How big of an earthquake is the Pacific Northwest capable of experiencing?
It is now thought to be capable of producing great earthquakes of magnitude 8 or 9, like those off Indonesia in 2004 and Japan in 2011. Before the mid-1980s, the tsunami hazard to the Pacific Northwest coast was thought to be from distant tsunamis, those that would come from afar with hours for warning and evacuation.
How scientists know when the last big Cascadia earthquake happened?
How could scientists know for sure? American researchers used carbon dating on the spruce, peat and fossilized plants. Sitka spruce as far apart as southern Washington and Northern California died from the high waters during the same few decades — sometime between 1695 and 1720.