Japanese shipwreck adds to quake evidence

SEATTLE, Oct. 31 (UPI) -- A Japanese shipwreck in 1700 may finally establish a great earthquake tore the sea floor off the coast of Washington the same year.

Experts at the University of Washington in Seattle say written records collected from villages along a 500-mile stretch of the main Japanese island of Honshu show the coast was hit by a series of waves, collectively called a tsunami, on Jan. 28, 1700.

Because no Japanese earthquake warned of the waves, it is likely they came from somewhere else around the Pacific Rim, says Brian Atwater at the university.

"This is the only account that is nautical, and it is the only one in which the tsunami contributed to deaths," he said.

The ship, which was wrecked by the storm, carried nearly 30 tons of rice bound for Tokyo.

"It seems the tsunami lasted 18 hours at least, and that's another hint that the earthquake that caused it was very big."

The storm drove the ship into coastal rocks, two crew members died and all the rice was lost.

The size of the 1700 tsunami in Japan implies that quake was in the range of about 9.0, Atwater said.

That quake is believed to have ruptured more than 600 miles of the boundary between the Juan de Fuca and North American tectonic plates, which meet off the Pacific Northwest coast in what is called the Cascadia Subduction Zone.

At a magnitude of 9.0, the energy generated by the 1700 quake would have exceeded the total amount of energy currently consumed in the United States in a month, Atwater said.