A weekend earthquake in Southern California has unlocked one of the most dangerous fault lines that could soon produce a devastating seismic disaster, a geophysicist has warned. The US Geological Survey (USGS) reported that a magnitude 4.1 quake struck less than 70 miles north of Los Angeles at 12.53pm ET (9.53am local) on Sunday. While the quake itself was relatively small and did not lead to any reported injuries, geophysicist Stefan Burns warned that this seismic event occurred at a rare junction linking the Garlock Fault to the infamous San Andreas Fault. The Garlock is a major east-west fault in Southern California, while the San Andreas is an 800-mile-long fracture running from Southern California north through the Bay Area and into the Pacific Ocean. Burns warned that the earthquake struck exactly where these two faults meet, in an area that has not seen a quake this strong in more than 26 years. According to the scientist, this small event at the junction could be an early sign that underground stress is building and the Garlock may play a role in the next major California earthquake - which many call 'The Big One.'

'The Big One' is the nickname for a future earthquake, likely stronger than magnitude 8, that researchers fear will be so enormous that it would devastate the West Coast as it spreads along the San Andreas. Burns explained that because the Garlock and San Andreas meet at this exact junction, a major rupture on the Garlock could quickly jump to the much longer San Andreas, sending a crippling mega quake throughout Southern California. Burns said: 'We already know that the Garlock is locked and loaded for a big rupture. Could be magnitude 7 or higher, magnitude 7.5 or greater even.'

'If you get an earthquake right there, hitting precisely the point where the two meet, and we haven't seen an earthquake of that magnitude strike that area in at least 26 years. You know that something's evolving here.' Burns, a science communicator who is now the founder and CEO of holistic wellness company Earth Evolution, noted several key reasons why the magnitude 4.1 quake could be a foreshock for the Big One. Previous studies of the San Andreas and other faults in California have concluded that there is a 99 percent chance of a major quake stronger than magnitude 6.7 by the year 2043.

Experts with USGS have predicted that a massive earthquake striking under Los Angeles would cause hundreds of deaths, tens of thousands of injuries and $200 billion in damages. Burns explained that both the Garlock and San Andreas are strike-slip faults, places where two massive blocks of the Earth’s crust slide horizontally past each other, like two tractor-trailers driving side-by-side in opposite directions on a highway. While the Garlock moves to the left, the San Andreas moves to the right, with both fractures meeting near California's Frazier Park, creating a complicated 'push and pull' zone at a noticeable bend in the San Andreas.

However, rocks often get stuck, or locked up, as Burns said, instead of sliding smoothly past each other. Over decades or centuries, enormous stress and energy build up in the locked sections, especially near this bend in the San Andreas. When the stuck parts finally slip suddenly, it releases all the stored seismic energy as an earthquake, which, in the Garlock Fault's case, could trigger a major rupture producing an event close to magnitude 8. 'The Garlock fault is heavily locked up. It hasn't had a major rupture. Think magnitude 7.5 for 500 to a thousand years,' Burns said in a July 12 episode on his YouTube channel. The geophysicist added that both the San Andreas and Garlock are both considered 'overdue for big ones, magnitude 7.5 or greater.' Although Burns said the USGS data showed Sunday's quake striking 'exactly on' the San Andreas-Garlock junction, seismologists at the Southern California Seismic Network have disputed this claim. Their readings suggest that the 4.1 magnitude quake occurred on the nearby Pleito Fault, just 5,000 to 15,000 feet away from the junction. If true, it would likely mean there was no direct rupture along the two major faults.

However, scientists have previously warned that this part of Southern California is still under extreme stress, with the San Andreas experiencing its highest levels of seismic stress in 1,000 years. In June, Liliane Burkhard from the University of Hawaiʻi at Mānoa said: 'Right now, with stress at historically high levels across the region and more than 160 years having elapsed since the last major rupture, the system is in a critically loaded state.' Burns suggested that there may be a strange link between seismic activity on Earth and solar flare activity, pointing out that a strong solar flare erupted just hours before the earthquake near Los Angeles. He explained that solar flares blast out intense energy and charged particles that can strongly energize the ionosphere, the upper layer of our atmosphere, when they strike Earth. The scientist theorized that these electromagnetic and energetic changes in the atmosphere could subtly influence the Earth’s crust, possibly by adding tiny stresses or electrical effects to the already tense fault zones. 'It's not necessarily a sign that "okay, in the next two hours we're going to have the big one," but certainly it is just a little bit more evidence that there are more interconnections with the Earth and the sun and other places on the globe altogether than maybe most people realize,' Burns said.