Up here in Oregon, there seems to be a pretty good explanation for some of the relatively small to medium earthquakes we've had off the coast.
There's an underwater volcano erupting some 300 miles off the coast. It's. On the Axial Seamount and is being pretty closely watched by Oregon State: "Axial Seamount is unique in that it is one of the few places in the world where a long-term monitoring record exists at an undersea volcano – and we can now make sense of its patterns,” said Chadwick, who works out of Oregon State’s Hatfield Marine Science Center in Newport, Ore. “We’ve been studying the site for years and the uplift of the seafloor has been gradual and steady beginning in about 2000, two years after it last erupted." So when you are looking for shells on the cold foggy beaches near Newport, just think that one of the small tremors was a wall of the seamount dropping eight feet.