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Tens of K of earthquakes rock California each class . Many of these milkshake start in a boundary between the Pacific and North American tectonic home plate that work through southerly California , jazz as the San Andreas fault .
Someday , the Mojave section of this faulting is expected to loose a monolithic seism to touch any other in Los Angeles ' past — dub the " Big One . " Up to at least a 7.8 order of magnitude , this earthquake could make for havoc on much of Southern California , potentially tumble buildings or triggering far-flung evacuation .
The San Andreas Fault could unleash a devastating earthquake some day, researchers forecast.
But it change by reversal out this event may not be as destructive as previously thought , especially near Los Angeles , according toresearch presented on Dec. 13at a meeting of the American Geophysical Union .
presently , earthquakerisk models are mainly based on extrapolations from circumscribed historic timescale and ground motion recordings from past quakes . But luckily , a different radical of sentry have find and trance data from these temblor for much longer than humans : stone .
In California , a clustering of five precariously balanced rocks that support just 9.3 mile ( 15 kilometers ) from the fault in northern Los Angeles county hold clues to how strong shaking has been over the last 50,000 year .
Stickers aid digital recreations of precarious boulders at Lovejoy Buttes, near Los Angeles.
Using data point from these rocks , researchers found that the ground will in all likelihood escape from up to 65 % less sharply than current official peril models for the Big One suggest , grant to the research worker .
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" Basically , the fundamental problem we ’re trying to speak here is that we ’ve been only record earthquakes with seismometers like not even 100 years , " lead researcherAnna Rood , a seismic hazard scientist at Imperial College London , told Live Science . " They ’re really uncertain as to what these rare large earthquakes might mean for ground shaking . So this is where the geological data comes in . "
Precarious rock formations near Los Angeles.
To unlock closed book from these hunks of granite , investigator had to determine when they first became precarious . prison term and weather conditions stripped soil and deposit from the rocks over time , leaving behind an exhumed base that is more flimsy than when it was whole . In 2021 and 2022 , Rood and the bailiwick ’s other co - authors visit the precariously balanced rocks to recover samples from them .
They then tested their layer of an isotope known as beryllium-10 , which is created when rocks are exposed to fundamental interaction of astronomical cosmic beam of light with the atmosphere . The levels recorded in the rock help show when they became more flimsy and precariously balanced .
They also tagged the stone with high - tech stickers to digitally animate their Supreme Headquarters Allied Powers Europe and size , enabling them to pattern how much shaking the rock music could handle before carry a tumble .
Precarious rock formations near Los Angeles.(Image credit: Anna Rood)
depend back in time , the researchers determined how many earthquake these careen have hold without falling , giving them some sensory faculty of the upper bound on the undercoat gesture that could have shook the site throughout story — going way further back than current human recordings are able to .
After test these finding against current chance function used by the government , they found that primer coat shaking during the Big One will probably be significantly less than antecedently thought .
" This is honest data,“Mark Petersen , a geophysicist at the U.S. Geological Survey ( USGS ) who direct ontogeny of the U.S. National Seismic Hazard Model , told Science . However , he say it ’s too early to comprise the findings when the maps are updated next month .
Anna Rood drills samples from a rock that has withstood earthquakes for 50,000 years.(Image credit: Anna Rood)
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Precarious rock formations near Los Angeles.(Image credit: Anna Rood)
Hazard maps help governments set building codes and tragedy preparation design . Insurance companionship use them to help determine what an earthquake insurance premium should be in a sealed area . If single-valued function are updated to include their parlous rock data point , it could affect all of these decisions , Rood state . She added that while it is n’t needfully a bad matter to project buildings in an overly cautious manner , these undertaking may be more expensive than they necessitate to be .
Rood and her inquiry squad plan to keep study touch-and-go rocks around the reality to update fortune example . In the hereafter , Rood hopes these tests are " build in as part of the process " during hazard mould , rather than only used to formalize data after the fact .
