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“Over the past 10,000 years, there have been 19 earthquakes that extended along most of the margin, stretching from southern Vancouver Island to the Oregon-California border,” Prof. Goldfinger stated in a summary of the study. “These would typically be of a magnitude from about 8.7 to 9.2 — really huge earthquakes.”

He added that the southern margin of Cascadia, encompassing southern Oregon and Northern California, “has a much higher recurrence level for major earthquakes than the northern end and, frankly, it is overdue for a rupture.”

But he cautioned: “That doesn’t mean that an earthquake couldn’t strike first along the northern half, from Newport, Oregon, to Vancouver Island.”

Co-author and OSU geologist Jay Patton also emphasized the likelihood of a major quake in the Pacific Northwest in the coming decades.

“By the year 2060, if we have not had an earthquake, we will have exceeded 85% of all the known intervals of earthquake recurrence in 10,000 years,” he said in the overview. “The interval between earthquakes ranges from a few decades to thousands of years. But we already have exceeded about three-fourths of them.”

The second study, which appears in the latest issue of the journal Geology, interprets new fault-zone temperature data along the Pacific Coast to conclude that the probable impact area of the next megathrust quake in the region could extend as much as 55 kilometres farther east than previous studies have suggested — raising the spectre that coastal cities such as Vancouver, Victoria, Seattle and Portland would experience significantly greater-than-expected seismic impacts when the next “Big One” strikes.