Peninsula Daily News news sources
Over the past 3,000 years, almost every major earthquake on California’s San Andreas fault was closely linked in time with an earthquake on the Cascadia subduction zone, an offshore fault off the Olympic Peninsula, new research shows.
Generally, the Cascadia quakes preceded the California quakes by 25 to 45 years.
“It’s either an amazing coincidence, or one fault triggered the other,” said Chris Goldfinger, associate professor of marine geology and geophysics at Oregon State University.
“Even if the details are fuzzy — something is going on.”
He and his colleagues published their research in the April issue of the Bulletin of Seismological Society of America this week.
The team also found evidence that the southern part of the Cascadia fault may unleash earthquakes much more frequently than previously believed — about every 200 to 240 years rather than every 500 to 600 years.
The last major quake along the entire Cascadia fault — which stretches from Vancouver Island to Northern California — occurred in 1700.
It dropped parts of the Olympic Peninsula coast by five feet and triggered a tsunami that pounded the Pacific Northwest and washed away houses in Japan.
“It’s been 308 years since the last one,” Goldfinger said. “We’ve actually exceeded the average repeat time for the southern half.”
Geologists used to scoff at the possibility that earthquakes could beget other earthquakes on distant faults, but no more.
In 1992, an earthquake in the Mojave Desert was followed almost immediately by a dozen quakes as far away as Wyoming.
A 2002 quake in Alaska caused geysers to spew in Yellowstone National Park.
“The Earth is like a puzzle, and any time one piece moves, it interacts with other pieces,” Goldfinger said.
