The mother of all Tsunamis

Geologist have recently found evidence that a Pacific Northwest earthquake may have sent waves of 15 foot tsunamis across the ocean to devastate Japan, some 300 years ago. The scientist substantiate this finding with the finding of a massively powerful earthquake zone, offshore from Seattle, that runs 600 miles up the Pacific Coast from Northern California to southern British Columbia. The zone is thought to be inactive, but we have seen how some inactive volcanos behave. The quake that hit 300 years ago was estimated to be in the magnitude 9 category.

Quakes of that size are quite rare. If a quake of this size were to strike today, hardly anything would be left standing.

Atwood said the geological record indicates the fault ruptures about once every 500 years and is capable of unleashing “truly giant earthquakes.”

He said only three quakes this century compare in magnitude — a 9.0 quake in Kamchatka in 1952, a 9.5 quake in Chile in 1960 and a 9.2 trembler in Alaska in 1964.

“The 1906 earthquake (in San Francisco) was a very big earthquake, but this thing in 1700 was in a different class,” said Atwood.

He said the fault, which is long and slopes gently under the North American tectonic plate, is characterized by tremors that last for several minutes. “It is very challenging for building design,” he said. “Most earthquakes don’t last that long. We have no experience for building to withstand it.”

The quake that hit 300 years ago is nothing but a Native American legend, but in Japan, the tsunami was well-documented.

“It flooded farmed fields, ruined salt kilns, damaged fishermen’s shacks, ascended a castle moat, entered a government warehouse, drove people to high ground, and probably ran 2 kilometers up a river,” the paper says. “It wrecked houses not only by flooding them but also by starting a fire. It contained multiple waves that range in reported time from midnight until the following noon. The tsunami initiated a nautical accident in which were lost two crew members and tons of rice.”

I have been through a few earthquakes, ranging in magnitude from 3 - 6, and all are a bit unnerving. I just can’t imagine what a magnitude 9 would be like, nor do I wish to know.