A swarm of moderate earthquakes has struck California, sending shockwaves in all directions for over 100 miles.
The US Geological Survey (USGS) detected the first and largest of the quakes at 4.10pm ET Tuesday afternoon between the cities of Willits and Ukiah, measuring 4.4 in magnitude.
The epicenter was approximately 120miles north of San Francisco, the region's largest major city.
Seismic maps of the incident revealed that the 4.4 tremor rippled all the way to the San Francisco Bay Area, sending out light shaking up and down the coast.
The quake was quickly following by three minor tremors, measuring at magnitude 1.7 at 4.16pm, magnitude 1.5 at 4.21pm, and magnitude 1.4 at 5.14pm.
Nearly two hours after the first earthquake, USGS reported that a magnitude 3.7 seismic event was detected at 5.51pm.
The sizable quakes were centered in a seismically active part of the state roughly 10miles from Northern California's Maacama Fault.
The Maacama is an active fault line in the region that can cause strong shaking and damage in areas like Mendocino and Sonoma counties, where it runs through rural communities and wine country.
Making the fault even more of a concern to locals is the fact that it's part of the larger San Andreas Fault system, the infamous 800-mile-long fault running through much of California.
The 4.4 quake struck less than five miles beneath the surface, which is shallow enough to cause a significant amount of shaking at ground level.
USGS scientists have documented that the Maacama Fault has produced large earthquakes in the past and could potentially generate one in the future which could exceed magnitude 7.0 in strength.
Tuesday's quakes have renewed fears that a major earthquake is not only possible in Northern California and the Bay Area, but is nearly guaranteed to erupt within the next 20 years.
