© USGS
The quakes were well beneath the ocean and there were no initial reports of damage or injury. The NOAA reported that no tsunami was expected from the quakes.
The two morning earthquakes struck two days after a magnitude 7.9 quake in the Gulf of Alaska, which resulted in a tsunami watch that was later canceled.
The 5.8 earthquake struck at 8:39 a.m. about 115 miles west of Eureka, Calif., at a depth of 5 kilometers. The closest quake to shore came at 9:24 a.m. and had a magnitude of 5.0, according to the USGS. That one had a depth of 4 kilometers and was about 112 miles west of Ferndale.
"Historically this is a very active area, " said Keith Knudsen, deputy director of the Earthquake Science Center at the USGS. He said the quakes occurred at "the boundary between two plates that are moving relatively fast, past each other and we call this area the Mendocino Triple Junction, which implies there are three plates, and there are, but these particular quakes occurred in a boundary between two plates."
Comment: Over the past seven days, California has experienced 15 earthquakes of magnitude 2.5 or greater up and down the state, including the two that hit off the coast in the Pacific Ocean. The California coast is part of the "Ring of Fire," an area where there are an abnormal number of underwater volcanoes. Made up of the Pacific coastline of the U.S., Asia and the Pacific Islands, this area is prone to earthquakes. There has been an uptick in seismic and volcanic activity in this region recently. See also: String of earthquakes and volcanic eruptions hits Ring of Fire - at least five events in two days