Quake data indicates a not-so-big one

PORTLAND – Using hand-me-down technology from the Cold War, scientists have discovered that the seafloor off the Pacific Northwest is a jumping kind of place, with thousands of small, swarming earthquakes and tectonic plates that are slowly rearranging themselves.

The findings could mean that a “big one” earthquake may not be as severe as previously thought, the lead researcher said.

An article in the journal Geology by researcher Robert Dziak describes the findings. Dziak is an associate professor at Oregon State University who also works for the National Oceanic Atmospheric Administration. He’s stationed at OSU’s Hatfield Marine Science Center in Newport.

Dziak’s article describes both new data and a record of earthquakes going back more than a decade. Much of the data was collected using once-secret Cold War “hydrophones” the Navy employed to track submarine movements in the Pacific Ocean. Dziak said the Navy controls the system of seafloor microphones and relays the data to Newport.

He said tectonic plates off the Pacific Northwest appear to be rearranging themselves and slowly jamming into each other. Dziak said one boundary among them appears to be turning into a fault that’s more like the San Andreas Fault to the south in California. Instead of ramming together, the plates are rubbing past each other, he said.

Emphasizing that the conclusions are tentative, Dziak said the consequence could be a shortening of the fault along the Pacific Northwest, so a major earthquake wouldn’t be so extensive or severe.

The rearrangement could limit the potential for a magnitude 9 earthquake, he said.