There were few indications on social media that the quake was strongly felt, if at all. Neither the Eureka nor Fortuna police departments reported that they felt anything or received reports of damage.
Within 20 seconds of the larger quake, the USGS reported on its website a 5.6 magnitude temblor that was closer to the California coast, but deleted it later.
“There was only one event, and that was the 5.7,” said Justin Pressfield, a spokesman for the USGS.
Pressfield said there was a discrepancy in different scientific networks’ reading of the data from the earthquake, which resulted in a mistaken reporting of two quakes.
According to the USGS website, the quake was felt by a some people in the greater Eureka area.
That quake was followed by a 3.9-magnitude aftershock.
A smaller 3.3 earthquake did occur beneath the Pacific in the same general area around 10 a.m., however.
California’s north coast is one of the state’s most seismically active areas, regularly producing major earthquakes. There had been other smaller quakes in the area in recent days.
In January 2010, a 6.5 quake hit the area, snapping power lines, toppling chimneys, knocking down traffic signals, shattering windows and prompting the evacuation of at least one apartment building.
A 6.9 earthquake struck the same area in 2014, and a 6.5 quake hit last December.