California rocked by SEVEN earthquakes in less than 24 hours

California rocked by SEVEN earthquakes in less than 24 hours

STACY LIBERATORE

California has experienced seven earthquakes in less than 24 hours, with the latest striking Friday morning.

The US Geological Survey (USGS) detected five quakes along the San Andreas faultthat experts say is overdue for a magnitude 8.0 or higher, known as the 'Big One.'

The initial event, a magnitude 2.7, hit Thursday off the coast of Northern California, followed by another magnitude 2.5 less than one hour later in the same region.

A 2.9 quake was detected near the cluster Friday, another 2.7 magnitude  northwest of San Diego and the latest clocked in as a magnitude 2.6.

The other two earthquakes struck near Death Valley, along the Foothills fault system, with a magnitude 3.0 detected on Friday. 

The other was a smaller 2.6 quake that hit Thursday.

While the earthquakes are not considered major, more than half of them hit along San Andreas, which 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. 

The last major earthquakes on the San Andreas fault were in 1857 and 1906.

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.

 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.

The Foothills fault system sits in the Sierra Nevada mountains, several tens of miles away from San Andreas.

The last notable earthquakes on the Foothills fault system were damaging events occurring in 1975 near Oroville and 1909 and 1888 near Nevada City.

These seismic events ranged between magnitude 5 to 6.