April 8 2014 – The 1700 Killer Cascadia Earthquake: On January 6, 1700, at about 9:00 p.m. Pacific Standard Time, a gigantic earthquake occurred sixty to seventy miles off the Pacific Northwest coast. The quake violently shook the ground for three to five minutes and was felt along the coastal interior of the Pacific Northwest. A tsunami formed, reaching about 33 feet high along the coast, and then traveled across the Pacific Ocean and hit the east coast of Japan.
Note: A 9.0 magnitude earthquake near Vancouver and Seattle today would be biblical, in terms of the damage and destruction it would cause. A subduction zone tsunami generated just off-shore would give little warning time, coupled with pyroclastic flows of Mount Rainer. The West Coast of North America would be severely damaged and throw the Country and World in global depression.
The earthquake ruptured what is known as the Cascadia subduction zone – the area of overlap between two of the tectonic plates that make up the earth’s surface. These plates are the Juan de Fuca and the North American. The Cascadia subduction zone extends from Vancouver Island, British Columbia south to Cape Mendocino in Northern California. The earthquake dropped the entire Pacific Northwest ocean coastline three to six feet.
The tsunami traveled across the Pacific Ocean for some 10 hours and at midnight on January 27, 1700, local time, it hit the east coast of Japan. By then the tsunami was only 6-10 feet high but it still did significant damage.
The very existence of this magnitude 9 earthquake was unknown just twenty years ago. An early breakthrough came in 1987 when U.S. Geological Survey geologist Brian Atwater reported geological traces of giant earthquakes along Washington’s Pacific coast. These traces included groves of trees that were killed when an earthquake lowered forests into the salt water. Another important clue was reported a few years later when the earthquake was dated to the decades between 1680 and 1720. This clue came from radiocarbon tests by Minze Stuiver of the University of Washington. Meanwhile in Japan, several researchers were following these developments. They consulted their nation’s archives of old writings about earthquakes and tsunamis. For the period between 1680 and 1720 they found one orphan tsunami that could have come from Cascadia. That tsunami occurred in January of 1700. Finally, a final clue was found in the groves of killed trees on the Washington coast. Using annual growth rings in the trees, David Yamaguchi of Seattle and Gordon Jacoby of Columbia University showed that the trees lived through the 1699 growing season but were dead by the following spring – exactly the dates expected if the earthquake occurred in January 1700. (Credits – Wikipedia and the New York Times).
The Master of Disaster