The tremor, which occurred 215 miles (350 km) northwest of San Francisco, severely damaged many roads.
JB Mathers, a local of the seaside community of Eureka, claimed that "everything that was attached to the walls fell off the structures."
Authorities have cautioned the public to prepare for aftershocks and shuttered a number of routes.
Tuesday at 10:34 GMT (02:34 PST), the earthquake occurred. According to the US Geological Survey, it gave rise to up to 80 minor earthquakes with magnitudes between 4.6 and 2.5.
11 individuals were hurt in addition to the two fatalities, according to the sheriff's office for Humboldt County.
Gas pipes were broken by the tremor, leading to leakage. Two more buildings collapsed while one structure caught fire and was promptly put out.
As per the monitor (Power outages), more than 32,000 consumers still didn't have power as of Tuesday evening local time.
The tremor, which happened about two miles off the coast, had not been anticipated to cause a tsunami, according to the sheriff's office.
Authorities continue to evaluate the damage. Power restoration in the isolated, densely forested area, according to utility personnel, might take days.
Report of the prevalent situation
According to CBS, the BBC's US partner, the Highway Patrol of California has closed the Fernbridge, a 1,320-foot (400-meter) concrete arch footbridge over the Eel River, after finding four fissures.
Power went out and there was broken glass all over the streets of Fortuna. Due to the potential that pipelines in the region have been polluted by groundwater sources, locals have been advised by officials to boil their water.
A lesser earthquake with a 3.6 magnitude occurred in the San Francisco area on Saturday, inflicting minor economic and environmental damage and waking up hundreds of individuals early in the morning.