Potential Arrival of the Big One
While these recent quakes are significantly weaker than historic ones like the 6.7 magnitude Northridge Earthquake of 1994, which caused an estimated $20 billion in damage and killed over 57 people, they raise concerns about the potential arrival of the so-called Big One in a state with numerous active fault lines.
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The infamous 800-mile-long San Andreas Fault, which runs from near the Mexico border, east past Los Angeles, and up the coast north of Sacramento, is a particular worry.
60 Percent Chance of Magnitude 6.7
Major quakes occur along this fault approximately every 180 years, yet it hasn’t seen a powerful one since 1906.
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The US Geological Survey estimates there is a 60 percent chance of a magnitude 6.7 or greater quake hitting the Los Angeles area in the next 30 years.
Overdue for a Big Earthquake
Even more concerning is the Cascadia Subduction Zone, stretching from Northern California to British Columbia, Canada, which is overdue for a significant earthquake based on historical averages.
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So, do the recent earthquakes signal something larger? Are they just routine in a state that experiences about 35 quakes a day?
DTLA & OC
The El Sereno quakes, for instance, occurred just beneath the Puente Hills thrust fault, which runs under downtown Los Angeles and Orange County.
Source: EEJCC, Wikimedia
This fault angles like a ramp, coming closest to the surface near the LA campus of the University of Southern California.
Ten Times the Intensity
An earthquake here could amplify the intensity up to ten times more than in areas located on bedrock.
Source: Wikimedia
The Newport Beach-Costa Mesa quakes occurred near the Compton thrust fault, which could raise the LA River by up to 5 feet in a strong quake, severely impacting city sewer systems.
San Andreas Fault - Sparsely Populated
Geologists note that there have been six quakes above magnitude 7 along this fault in the last 12,000 years.
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Scientists emphasize that instead of focusing solely on the magnitude of the largest quakes, it’s crucial to consider the potential damage to densely populated areas. The San Andreas Fault, despite its notoriety, largely runs through sparsely populated desert regions.
Significant Damage
“In some respects, the ‘big one’ in terms of damages and deaths would be ones running through town rather than one that’s a long distance away,” Dr. Pat Abbott, professor emeritus of geology at San Diego State University, told KSWB last year.
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He highlighted major quakes like the 1857 and 1906 San Andreas earthquakes and the 1994 Northridge earthquake, all of which were below the 8.0 magnitude considered in “Big One” scenarios but still caused significant damage.
Difficult to Predict Exact Earthquakes
The California Governor’s Office of Emergency Services website states, “Unfortunately, earthquake prediction remains an extremely challenging endeavor. While scientists can monitor fault lines and detect patterns of seismic activity, they cannot predict exact earthquakes reliably.”
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Instead, scientists focus on long-term probability to help high-risk areas prepare for the possibility of a major quake.
“Holy Grail” of Earthquake Science
For example, the USGS estimates a 72 percent chance of a 6.7 or greater magnitude earthquake hitting the San Francisco Bay Area within the next 30 years.
Source: Wikimedia
Achieving a higher level of precise prediction is considered the “holy grail” of earthquake science, according to University of Washington seismologist Harold Tobin.
Not Yet There
“Science has not yet found a way to make actionable earthquake predictions,” Tobin wrote last year.
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“A useful prediction would specify a time, a place and a magnitude – and all of these would need to be fairly specific, with enough advance notice to be worthwhile.”
Preparedness is Key
Until such precise predictive methods are developed, governments can enhance preparedness through measures like digital alert systems, practice drills, and building retrofits.
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Meanwhile, individual citizens should have emergency kits ready and follow safety protocols, such as dropping to their knees, covering their head and neck, and holding onto something stable when an earthquake starts.