Importance Score: 85 / 100 🟢
Southern California Earthquake Risk: Lesser-Known Fault Zone Sparks “Big One” Concerns
A significant earthquake in Southern California this week has renewed anxieties about the potential for a catastrophic “Big One,” but experts suggest it may originate from an unexpected source: the Elsinore fault. While much attention is given to the San Andreas fault, this lesser-known seismic zone poses a considerable threat to the region.
Elsinore Fault: A Major Seismic Zone
The Elsinore fault, a branch of the well-known San Andreas fault system, stretches for over 100 miles across Southern California. It traverses a densely populated area, extending from the US-Mexico border through San Diego and Riverside Counties, reaching towards Los Angeles. The California Institute of Technology has identified the Elsinore fault, located just 15 miles from San Diego County, as one of Southern California’s most extensive fault zones.
Quiet History, Potential for a Major Earthquake
Despite its relative quietness in recorded history, seismologist Lucy Jones cautions that the Elsinore fault remains capable of generating a substantial earthquake, potentially reaching a magnitude of 7.8. The last major seismic event exceeding magnitude 6.0 along the Elsinore fault occurred in 1910. However, data from the US Geological Survey (USGS) and the Southern California Earthquake Center indicates that such events typically occur every 100 to 200 years.
Rising Seismic Activity Raises Alarm
“The Elsinore fault represents a significant hazard in Southern California,” Jones stated following the recent 5.2 magnitude earthquake near San Diego. She added, “Over the past few years, we’ve observed a greater frequency of felt-earthquakes compared to previous decades.” This apparent increase in seismic activity has prompted the USGS to develop projections illustrating the potential devastation of a major earthquake originating from the Elsinore fault, contrasting it with scenarios focused solely on the San Andreas fault.
Simulating a Catastrophic Earthquake on the Elsinore Fault
The USGS simulation of a 7.8 magnitude earthquake along the Elsinore fault depicts potentially devastating consequences, with widespread damage likely extending from San Diego to Los Angeles and possibly beyond. The Elsinore fault, while distinct, is interconnected with the broader San Andreas fault system, a network of faults accommodating the movement of tectonic plates in California. It runs parallel to and east of the San Andreas fault in Southern California, spanning approximately 110 to 150 miles from the US-Mexico border through San Diego County.
vCard.red is a free platform for creating a mobile-friendly digital business cards. You can easily create a vCard and generate a QR code for it, allowing others to scan and save your contact details instantly.
The platform allows you to display contact information, social media links, services, and products all in one shareable link. Optional features include appointment scheduling, WhatsApp-based storefronts, media galleries, and custom design options.
Elsinore Fault Linked to Recent Seismic Events
Dr. Jones confirmed that the recent seismic event was associated with activity along the Elsinore fault line. She elaborated, explaining to KCAL News, “The Elsinore is considered a ‘junior sister’ to the San Andreas. As the San Andreas enters Southern California, it branches into four parallel faults: the San Andreas, the San Jacinto, the Elsinore, and the Newport-Inglewood.”
Potential Damage Reach Extends to Los Angeles
Although major earthquakes occur less frequently along the Elsinore fault compared to others, seismologists warn that a significant event could inflict damage extending as far as Los Angeles, a major metropolitan area home to nearly four million residents. In 2017, the USGS conducted a simulation of a 7.8 magnitude earthquake originating on the Elsinore fault and propagating northwest towards the connecting Whittier fault line, which is closer to Los Angeles.
Los Angeles Under Threat from “Big One” Scenario
In this “Big One” scenario affecting Los Angeles, the simulation predicted intense shaking and widespread structural damage to buildings and foundations. Utilizing the Modified Mercalli Intensity (MMI) scale for seismic activity, USGS researchers estimated that Los Angeles could experience MMI levels of 7.5 to 9.0 – nearing the upper end of the scale. Only levels 10 through 12 represent more extreme conditions, indicating “total destruction.”
San Diego’s Projected Earthquake Impact
Conversely, the hypothetical earthquake scenario projected a lower MMI range for San Diego, between 4.0 and 6.5. This level of shaking could result in strong tremors, cracked walls, collapsed chimneys, and some structural damage throughout the city. Overall, the assessment suggested that San Diego’s damage would be manageable, with a lower probability of widespread injuries.
Wider Impact: Injuries and Economic Losses
However, if a significant 7.8 magnitude earthquake were to propagate from the Elsinore fault to the Whittier fault, Los Angeles would face a high likelihood of injuries, fatalities, and substantial economic losses. Even cities as distant as Las Vegas, approximately 300 miles east of Los Angeles, could experience moderate shaking capable of causing minor damage, reaching an MMI of 4.5. The seismic forces are also projected to extend north, impacting cities such as Santa Barbara, Bakersfield, and Fresno, a region encompassing over 23 million people.
Decades of Quiet Followed Major Quakes
Jones noted that two significant earthquakes in the 1990s – the magnitude 7.3 Landers earthquake in 1992 and the magnitude 6.7 Northridge earthquake in 1994 – effectively reduced the local tectonic stress in Southern California for several decades. This period resulted in relatively low seismic activity. However, Jones suggests that the region is now showing signs of returning to the heightened seismic activity levels observed in the 1980s.
San Andreas Fault: Historical Devastation
Previous estimations concerning an earthquake approaching magnitude 8.0 on the Richter scale along the San Andreas fault projected potentially catastrophic consequences, including approximately 1,800 deaths and 50,000 injuries across California. The San Andreas fault traverses major urban centers including San Francisco, San Bernardino, and Palmdale, and passes near Los Angeles and Palm Springs. This extensive fault line, stretching over 800 miles, was responsible for the devastating 1906 San Francisco earthquake, estimated to have reached a magnitude of 7.9. That seismic event decimated 80 percent of San Francisco and resulted in over 3,000 fatalities.