The US Geological Survey reported that a 6.9-magnitude earthquake struck off the coast of Northern California on Sunday night.

The epicenter was 48 miles west-northwest of Ferndale and 50 miles west of Eureka at a depth of 4.3 miles, the USGS said.

The quake, which occurred at 1:18 a.m. ET, was initially reported as magnitude 6.1 on the Richter scale, but seismologists revised it upward to 6.9. It was followed by about a half-dozen aftershocks, including one of magnitude 4.6.

There were no reports of any damage or injuries though the quake was felt widely and strongly, according sheriff’s and fire officials in Humboldt County, which includes most of the populated areas near the epicenter.

The earthquake epicenter was 48 miles west-northwest of Ferndale and 50 miles west of Eureka at a depth of 4.3 miles

Police in Eureka said the shaking lasted between 20 and 30 seconds.

Earthquakes are very common in Eureka, a city of about 27,000 people about 270 miles northwest of San Francisco and 100 miles south of the Oregon state line.

The probability of a “strong and possibly damaging aftershock” of magnitude 5.0 or greater in the next seven days was 90 percent, the USGS warned, adding that there was a 5 percent to 10 percent of another quake as large as or larger than the initial one in the next week.

No destructive tsunami was expected, and no tsunami advisory was issued, The West Coast/Alaska and Pacific Tsunami Warning Centers said.

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