The quake struck about 50 miles west of Eureka and occurred at 10:18 pm Pacific Time, 4.3 kilometers below the seabed , according to the USGS.
It was followed by about a half- dozen aftershocks, including a magnitude 4.6 .
Not believed to be a threat of a tsunami , according to the Center for the Pacific Tsunami Warning .
Sheriff Humboldt County , which oversees most of the populated areas near the earthquake , says there have been calls of damage or injuries .
" This lasted longer than any earthquake I've ever felt ," Raquel Maytorena , 52 , who lives about a mile from the coast near Eureka Ferndale , told the Los Angeles Times. "It just kept going and going , very slowly and gently . Was not violent. It almost felt like you were in a boat that was rocking . "
Jana Pursley , a geophysicist at the National Earthquake Information Center , said that based on the tectonics of the area and past earthquakes , it was unlikely that damage or casualties.
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