California has experienced two earthquakes since 7:45am ET, with the largest measuring a 3.2 magnitude.
The US Geological Survey (USGS) detected the first quake, a 2.5 magnitude, near San Francisco, striking less than three miles outside of Alamo.
The epicenter, however, sits within miles of more than 100,000 people scattered across four towns.
The second hit in the Pacific Ocean, about 47 miles west of Petrolia.
This region has experienced several quakes in recent weeks.
An assessment from Michigan Tech University showed that people typically do not feel quakes with a magnitude of 2.5 or less.
Those from 2.5 to 5.4 are often felt but only cause minor damage.
No damages or injuries have been reported following the two earthquakes.
California has experienced two earthquakes since 7:45am ET with the largest measuring a 3.2 magnitude
Alamo sits on the Calaveras Fault, a branch of the San Andreas that spans 800 miles from Cape Mendocino in the north to the Salton Sea in the south.
The ‘Big One’ would cause roughly 1,800 deaths, 50,000 injuries and $200 billion in damages, according to the Great California Shakeout.
Experts are ‘fairly confident that there could be a pretty large earthquake at some point in the next 30 years,’ Angie Lux, project scientist for Earthquake Early Warning at the Berkeley Seismology Lab, told DailyMail.com.
The last major earthquakes on the San Andreas fault were in 1857 and 1906.
The Fort Tejon earthquake of 1857 was a 7.9 magnitude, which caused ground fissures in the Los Angeles, Santa Ana and Santa Clara Rivers.
Trees were uprooted, buildings were destroyed and two people were killed during the event.
The catastrophic 1906 San Francisco event was also a magnitude 7.9 earthquake, which killed 3,000 people and leveled much of the city.
Dr Sue Hough, a scientist in the USGS’ Earthquake Hazards Program, told KTLA5 that there are conflicting studies about what signs precede a major earthquake.
Some research suggested more activity happens before it hits, while others have found there is no warning, she added.
The US Geological Survey (USGS) detected the first quake, a 2.5 magnitude, near San Francisco, striking less than three miles outside of Alamo
California has had more than 6,200 earthquakes of magnitudes up to 4.7 this year alone, according to Volcano Discovery.
Approximately four quakes were above magnitude 4 and around 5,800 were below magnitude 2.
The vast majority of earthquakes result from the constant movement of tectonic plates, which are massive, solid slabs of rock that make up the planetary surface and shift around on top of Earth’s mantle — the inner layer between the crust and core.
As the tectonic plates slowly move against each other, their edges can get stuck due to friction and stress will build along the edges.
When that stress overcomes the friction, the plates slip, causing a release of energy that travels in waves through the Earth’s crust and generates the shaking we feel at the surface.
