The Big One  

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Clue Three: The Japanese connection

Carbon dating showed that the Washington and Oregon ghost forests had died between the years 1680 and 1720. Atwater reasoned that a massive earthquake in the Northwest could have killed the ghost trees. He also knew that such a large quake would generate tsunamis. These waves would strike all around the Pacific. So he looked to Japan for evidence, because Japan has some of the oldest written records of any country along the Pacific Rim.

Japanese researchers found records of only one large tsunami between 1680 and 1720. From maps and manuscripts, they learned that the tsunami had flooded several Japanese villages, including one called Otsuchi. If a Northwest earthquake had caused this tsunami, they calculated, the event would have taken place on the evening of January 26, 1700.

The town of Otsuchi, Japan, was damaged by a tsunami in 1700.
Otsuchi manuscript. In part, this manuscript states that the coastal village of Otsuchi was inundated by a “very high tide up to the houses behind the street.” Rice paddies, vegetable fields, and salt-evaporation kilns were damaged.

Clue Four: Tree ring evidence

Tree rings provided the last clue. Trees add rings of new wood each year. Good seasons produce wide rings, poor seasons produce narrow ones, or none. With this knowledge, scientists who study tree rings can date past events. Researcher David Yamaguchi found that the ghost forest trees were alive and healthy in late 1699, but dead by spring of 1700.

A tree’s growth rings (sets of light and dark lines) tell its age and something about the environment in which it lived. Dots show decades.

Clues add up BIG

From all these clues, researchers concluded that a huge earthquake had occurred 300 years ago along the entire Washington and Oregon coast. This Big One was a major subduction zone earthquake. A similar-sized quake could occur again at any time....

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