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decade of thousands of earthquakes rock California each year . Many of these waggle rise in a boundary between the Pacific and North American tectonic plate that melt through southerly California , hump as the San Andreas fault .
Someday , the Mojave section of this fault is expected to let loose a massive temblor to rival any other in Los Angeles ' past tense — dub the " Big One . " Up to at least a 7.8 magnitude , this earthquake could wreak mayhem on much of Southern California , potentially tip buildings or triggering widespread excretion .
The San Andreas Fault could unleash a devastating earthquake some day, researchers forecast.
But it turn out this event may not be as destructive as previously thought , especially near Los Angeles , according toresearch demo on Dec. 13at a meeting of the American Geophysical Union .
Currently , earthquakerisk models are mainly base on extrapolations from limited historic timescale and ground movement recordings from past quake . But fortunately , a dissimilar group of sentinel have witnessed and captured data point from these temblors for much farseeing than humans : rocks .
In California , a cluster of five precariously balanced rocks that bear just 9.3 miles ( 15 kilometers ) from the fault in northern Los Angeles county hold hint to how strong didder has been over the last 50,000 year .
Stickers aid digital recreations of precarious boulders at Lovejoy Buttes, near Los Angeles.
Using datum from these rock , researchers found that the ground will likely shake up to 65 % less aggressively than current prescribed peril model for the Big One intimate , grant to the research worker .
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" essentially , the fundamental trouble we ’re trying to address here is that we ’ve been only register earthquake with seismometers like not even 100 years , " head researcherAnna Rood , a seismic hazard scientist at Imperial College London , told Live Science . " They ’re really unsure as to what these uncommon large quake might mean for footing shaking . So this is where the geological information comes in . "
Precarious rock formations near Los Angeles.
To unlock closed book from these lump of granite , research worker had to determine when they first became shaky . metre and weather condition conditions stripped soil and sediment from the rock over clock time , leaving behind an exhumed base that is more fragile than when it was whole . In 2021 and 2022 , Rood and the study ’s other co - authors visited the precariously balanced rocks to retrieve samples from them .
They then tested their levels of an isotope hump as beryllium-10 , which is created when rock are exposed to interactions of galactic cosmic ray with the atmosphere . The levels recorded in the rocks helped show when they became more fragile and precariously balanced .
They also tag the rock with high - tech thorn to digitally revivify their shape and sizing , enable them to model how much stimulate the rocks could handle before taking a spill .
Precarious rock formations near Los Angeles.(Image credit: Anna Rood)
look back in clock time , the research worker learn how many earthquakes these rocks have withstood without fall , giving them some horse sense of the upper bound on the ground motion that could have shook the situation throughout history — go way further back than current human recordings are able to .
After testing these findings against current hazard maps used by the governing , they found that basis shake during the Big One will likely be importantly less than previously thought .
" This is good data,“Mark Petersen , a geophysicist at the U.S. Geological Survey ( USGS ) who lead growing of the U.S. National Seismic Hazard Model , told Science . However , he state it ’s too early to incorporate the finding when the maps are updated next calendar 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 function help governments position building code and disaster readiness programme . Insurance society apply them to help fix what an seism insurance policy premium should be in a certain area . If maps are updated to let in their precarious rock information , it could affect all of these decisions , Rood said . She added that while it is n’t needs a bad matter to project construction in an overly cautious fashion , these undertaking may be more expensive than they need to be .
Rood and her inquiry squad plan to keep on studying precarious rocks around the world to update hazard models . In the hereafter , Rood hope these tests are " built in as part of the process " during jeopardy modeling , rather than only used to validate data after the fact .
