A series of small earthquakes that rattled Salton Sea, a lake located directly on the San Andreas Fault, earlier this week increased the likelihood of a major quake hitting Southern California. The swarm prompted authorities to issue an earthquake advisory.
Seismologists from the U.S. Geological Services said that more than 140 seismic events, which ranged from magnitude 1.4 to 4.3, were recorded over a period of more than 24 hours since Monday morning.
The California Office of Emergency Services has issued a warning for those who live in Los Angeles, San Diego, Ventura, Orange, San Bernardino, Riverside, Kern and Imperial counties of the possibility of a major earthquake hitting the area over the next week.
Seismologists added that the chances of a magnitude 7 or greater earthquake occurring over the next week is between 1 in 100 to 1 in 3,000. Without the swarm, however, the average risk for such an event striking on any given week is 1 in 6,000.
The risk is anticipated to decrease over time but authorities urged people to always be on alert. OES Director Mark Ghilarducci said that California is an earthquake-prone country so residents always need to be prepared.
The swarm occurred in the Brawley Seismic Zone, which sits near a fault network that connects the Imperial fault and one end of the San Andreas Fault. Experts said that some cross-faults are positioned in a way that can possibly add stress to the San Jacinto Fault and the San Andreas Fault systems.
"This is close enough to be in that worry zone," said seismologist Lucy Jones. "It's a part of California that the seismologists all watch."
The southernmost stretch of the San Andreas Fault has not ruptured since about 1680. To put it in perspective, more than 330 years ago. Given that big earthquakes on average happen every 150 to 200 years, experts think that a major earthquake in the region is long overdue.
At the National Earthquake Conference in May earlier this year, earthquake experts warned that the San Andreas Fault is "locked, loaded and ready to go."
Los Angeles may not be located directly along the fault line but it will likely suffer from the impact of a major earthquake. According to a 2008 report from the USGS, a magnitude 7.8 quake on the southern section of the fault could result in more than 1,800 deaths and cost $200 billion worth of damages. Powerful earthquakes in the region are also feared to set off tsunamis.