The Columbian reported that a U.S. Geological Survey report said such quakes are common in areas around Mount St. Helens and Oregon's Mount Hood.
The latest southwest Washington quakes included a 3.7 magnitude jolt at about 2:30 p.m. Friday, followed by a 3.4 and a 3.1, both on Friday evening.
The quakes occurred at a depth of about 8 miles. There were no reports of damage.
The USGS said volcano-related seismic activity was at normal background levels.
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