4 Earthquakes Strike Oregon Coast Overnights
SALEM, Ore. (CBS SF) -- A series of earthquakes have struck off the Oregon coast but scientists say they weren't strong enough to trigger tsunamis.
The largest came first, at magnitude 5.8. It struck about midnight Sunday and was followed by three quakes early Monday. They were of magnitude 4.3, 5 and 4.4.
They struck at a fault nearly 300 miles west of Coos Bay, Oregon. They were relatively shallow, at 6 miles deep.
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Deeper quakes are less noticeable while a shallow quake--in the 0 to 40 mile depth range--can feel much stronger than their actual reported magnitude. Quakes just below the earth's surface, in the 0 to 10 miles range, can cause even more damage at lower magnitudes.
For example, the magnitude 7.8 quake that recently struck Japan did little damage because it was 420 miles deep.
Paul Caruso, with the U.S. Geological Survey, says the Oregon coast quakes were not big enough to trigger tsunamis. He says it usually takes a magnitude 7 for that to happen.
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Strong earthquakes with an epicenter off the coast can trigger tsunamis, depending on the size and type of the fault movement. The Pacific Tsunami Warning Center tracks earthquake data for the West Coast.
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