WASHINGTON — The western US state of Oregon has a 40 percent chance in the next half-century of suffering a massive earthquake on the scale of Japan's 2011 disaster, a study said Wednesday.
The Pacific Northwest -- from the Oregon-California border to Vancouver Island in Canada -- has endured 19 huge earthquakes of around 8.7-9.2 magnitude over the past 10,000 years, Oregon State University researchers said.
An additional 22 major earthquakes have impacted only the southern part of the so-called Cascadia fault that runs from the Oregon areas of Coos Bay to Newport, the study said.
"The southern margin of Cascadia has a much higher recurrence level for major earthquakes than the northern end and, frankly, it is overdue for a rupture," the study's lead author Chris Goldfinger said in a statement.
The study, published online by the US Geological Survey, estimated a 40 percent chance of a major earthquake around Coos Bay, Oregon, over the next 50 years.
It said that the earthquake could be on the scale of the 9.0-magnitude earthquake that struck in the Pacific Ocean near Japan on March 11, 2011. Some 19,000 people died as the tremor set off a devastating tsunami.
But Oregon has far fewer preparations in place than Japan, which is one of the world's most earthquake-prone nations.
The Oregon State University study billed itself as the most comprehensive yet, which is based on 13 years of research including assessments of sediment to determine past seismic events.
Oregon already had an oral history of earthquakes, with Native Americans speaking of a giant tremor in around 1700.
Earthquake preparedness has triggered a major political debate in Oregon, with advocates warning that many schools and other buildings would be woefully inadequate in the event of a giant disaster.
Critics say that the massive cost of upgrading Oregon's infrastructure could be devoted to more pressing priorities for residents such as building roads.