Two earthquakes hit Saturday near Government Camp, Oregon, one of them topping out at magnitude 3.9.
The tremors were strong enough for some locals to feel it, The Oregonian reported.
The earthquake rumbled at 8:51 p.m. June 5, just south of the summit of Mount Hood. It was preceded by several earthquakes in the hour before the quake, and tens of aftershocks have occurred since, the Cascades Volcano Observatory of the U.S. Geological Survey reported in a news release Saturday night.
The volcanic action and location are consistent with past swarms in the Mount Hood area, including a magnitude 4.5 on June 29, 2002, that was located about 1 mile east of Saturday's ground shaker.
Aftershocks will likely continue for hours or days, some of which may be felt, according to the news release.
Seismologists at the Cascades Volcano Observatory and Pacific Northwest Seismic Network advised they do not believe that this swarm signifies a change in volcanic hazard at Mount Hood. Scientists will continue to monitor the swarm.
For more on the 4,000-year history of eruptions in the Pacific Northwest's volcano country, see the Pacific Northwest Seismic Network information page.