Scientists fear replay
of historic disaster
A major earthquake in the
Cascade range could duplicate
the huge tsunami of 1700
Computer analysis of 300-year-old records from Japan and new information about the geology of the U.S. Pacific Northwest are raising concern that a giant earthquake in North America could trigger a widely destructive Pacific tsunami.
Scientists meeting in Seattle last month reported new discoveries about the link between a powerful 1700 U.S. coastal earthquake and a giant tsunami that hit Japan 10 hours later. Their full scientific paper on the study was published last month in the Journal of Geophysical Research-Solid Earth.
Records of a giant wave, flooding and damage in Japan have existed since the era of feudal shogun rulers, and some Japanese scientists theorized in 1996 that the calamity might have been caused by an earthquake in the western United States and Canada.
The new report includes details of computer simulations that scientists from Japan, Canada and the United States used to track the related calamities.
A dramatic animation posted on the Internet shows how the tsunami is believed to have roiled the entire Pacific, hitting Hawaii five hours later and Japan five hours after that.
The report pinpoints the North American earthquake to the morning of Jan. 26, 1700, based on Japanese records. It confirms that an earthquake close to magnitude 9 sent a tsunami across the Pacific, hitting Japanese shores with a wall of water calculated at up to 15 feet high.
The findings could affect preparations for future earthquakes and tsunamis around the Pacific Rim, the scientists said.
The possibility of an earthquake with a magnitude of 9 again hitting Washington, Oregon, northern California and southwestern Canada raises new questions about how to adjust building codes and tsunami-evacuation plans around the Pacific.
It could also help pinpoint the potential for future earthquakes.
"With a combination of a better understanding of the previous earthquake and modern observations, we hope to better define the potential rupture area of the future event," said Kelin Wang, of the Geological Survey of Canada, a co-author of the report.
Wang said scientists from the three countries are conducting seismic and geodetic monitoring along an enormous fault that stretches 600 miles along the coast from southern British Columbia to northern California. It is known as the Cascadia subduction zone, and Wang said it is "locked," building up for another possibly destructive event.
The scientists say the earthquake, which extended the entire length of the fault, unleashed as much energy as the United States now consumes in a month.
Along with Wang, lead authors of the report are Kenji Satake, of the Geological Survey of Japan, and Brian Atwater, of the U.S. Geological Survey, based at the University of Washington in Seattle.
The scientists said a series of discoveries since 1980 showed the fault has produced strong earthquakes up to magnitude 8 about every 500 years. Radiocarbon dating put the most recent between 1680 and 1720, coinciding with the Japanese data.
Satake and other Japanese researchers first reported on the possible link between the Japanese flooding and the American earthquake in 1996 in a letter to the journal Nature.
"As a result of this international collaboration," Satake said of the latest work, "we have collected more evidence, made rigorous interpretation of it and have modeled the earthquake source and tsunami propagation by using the latest techniques."