5.5 earthquake shakes offshore waters southwest of Eugene, no tsunami threat

A magnitude 5.5 earthquake struck the Pacific Ocean about 175 miles southwest of Eugene early Monday, centered 218 kilometers west of Bandon at 11:35:33 UTC on June 29, 2026, and about 10 kilometers deep. The U.S. Geological Survey marked the event as reviewed and showed three contributed responses, while no tsunami threat was issued and the initial record showed no reports of shaking on land.

A smaller 3.9 quake followed about an hour later in the same offshore area, and another 3.4 quake was recorded just after 6:30 a.m. Together, the quakes pointed to a short cluster of offshore seismic activity in the Blanco Fracture Zone, south of the Oregon coast.

The shaking landed in the broader Cascadia Subduction Zone, the 700-mile fault system that Oregon emergency managers say runs from northern California to British Columbia and sits roughly 70 to 100 miles off the Pacific coast shoreline. State officials say the last Cascadia megathrust earthquake happened on Jan. 26, 1700, with an estimated magnitude of 9.0, and scientists put the chance of a magnitude 7.1 or larger event there in the next 50 years at about 37 percent.

That larger hazard is why even a no-tsunami offshore quake matters in Lane County. Oregon emergency managers warn a Cascadia event could send a tsunami as high as 100 feet and leave communities without services for at least two weeks, a disruption that would reach far beyond the coast and into daily life in Eugene and across the Willamette Valley. Monday’s quake did not produce damage or a tsunami threat, but it offered a fresh check on how quickly the region can be reminded that the offshore fault system is active.