A swarm of small aftershocks pulsed through Northern California Friday morning in the wake of a major, 7.0 magnitude earthquake on Thursday, according to data from the U.S. Geological Survey.

Nearly 30 aftershocks were recorded on the USGS earthquake tracker within an hour’s drive of Petrolia, a small unincorporated community in Humboldt County.

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Thursday’s earthquake — called the 2024 Offshore Cape Mendocino California Earthquake — erupted some 40 miles offshore from Petrolia, and was believed to have occurred along the Mendocino Fault, one of the most seismically active parts of the state, according to experts.

“It’s been 35 years since the 1989 Loma Prieta earthquake that shook the Bay Area, and we are starting to forget,” said Paul Laustsen, a spokesperson for USGS. “It’s been a long time since we had a shaking of that magnitude.”

Several aftershocks since Thursday’s quake reached magnitudes over 4.0, which is considered small to moderate with the potential for damage, according to USGS.

Thursday’s quake was the strongest in the Humboldt County area since 1992. It spurred a tsunami warning Thursday morning that was canceled after the Tsunami Warning Center determined no danger existed along the West Coast.

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Experts said aftershocks could continue for several weeks, and the potential for a larger earthquake could not be ruled out.

“A lot of new people live in the area, so it’s important for people to be aware that we live in earthquake country,” said Laustsen. “We don’t know when a large earthquake is going to happen, but we know at some point it will.”