Two small earthquakes occurred near Angwin, just north of St. Helens, within minutes of each other on Tuesday.
A magnitude 3.6 earthquake occurred at 2:30 p.m. local time at a depth of 6.3 kilometers, or about 3.9 miles, followed by a magnitude 2.6 event in the same area three minutes later, according to the United States Geological Survey.
A short, strong shaking was felt at St. Helens, which is about five miles south of Angwin.
It was not immediately clear which fault caused the earthquake, but the West Napa fault zone and the Concord-Green Valley fault zone are located nearby.
Could the 3.6 magnitude earthquake be a harbinger of something bigger? Scientists say that, in general, with any earthquake, there is always a chance that this will happen. But the chances are very low and decrease over the days after an earthquake.