Lesser-known section of the San Andreas Fault could spare Los Angeles from the next 'Big One' earthquake
- Famous 800-mile system of fractures running much of length of California marks boundary between plates
- Scientists call main areas of tension 'strands', where collisions between plates produce dramatic landforms
- New research has revealed one of the strands which sees the highest levels of tension across the entire fault
- Means future earthquakes could be spread over a wider area, and tremors may be directed away from LAA a lesser-known section of the San Andreas fault in southern California may hold the key to sparing Los Angeles from the next 'Big One' earthquake, new research has found.
The 800-mile system of fractures running much of the length of California marks the boundary between the Pacific and North American continental plates, which produce earthquakes when they rub up against each other.
Scientists call the main areas of tension 'strands', where collisions between the two plates produce dramatic ridges and valleys as the land is crumpled like a sheet of paper - as seen below in newly-released images. Experts previously thought that most of the San Andreas Fault's movement occurred along the Banning and Garnet Hill strands some 100 miles east of LA.
But they have now discovered that another section, called the Mission Creek strand, sees even greater movement, and is thus at a higher risk of witnessing a quake.
This could be good for LA as it means tension is spread out over a wider area, rather than just in the areas covered by Banning and Garnet Hill, producing gentler tremors and reducing the damage they cause.
In addition, the orientation of the Mission Creek strand suggests it will not direct tremors into the LA metropolitan area, as could happen with the other two strands.
The San Andreas fault runs much of the length of California and marks the boundary between the Pacific and North American continental plates. Where the plates collide mountains form as the land crumples like a sheet of paper (pictured is a section near Mecca in southern California)
Scientists call the main areas of tension 'strands', where collisions between the two plates produce dramatic ridges and valleys like these ones seen in the hills near Mecca
Experts previously though that most of the San Andreas Fault's movement occurred along the Banning and Garnet Hill strands some 100 miles east of LA. But they have now discovered that another section called the Mission Creek strand sees even greater movement, and is thus at a higher risk of witnessing a quake. Pictured is the San Andreas fault near New Cuyama
A map showing the location of the Mission Creek, Banning and Garnet Hill strands. While the Banning strand is aligned east-west with the San Bernardino Valley, the San Gabriel Valley, and the Los Angeles Basin, Mission Creek has a north-westerly orientation. This suggests that some of the tremors from a quake would be diverted away from the Los Angeles basing, sparing the city some of the devastationThe San Andreas fault caused the Great 1906 San Francisco earthquake, when a 7.9 magnitude tremor destroyed 90% of the city and killed more than 3,000 people.
But the southern portion of the fault, which includes LA, has not seen a major earthquake since the 18th century, reports freelance geologist David Bressan in Forbes.
Strain produced by collisions between the Pacific and North American continental plates causes land in the southern portion of the San Andreas Fault to move around one inch per year, with any large movements producing earthquakes.
Researchers are able to understand which parts of the Fault are most at risk of an imminent earthquake by analysising how long ago the last one happened and how much tension has built up since.
Geologist Kimerly Blisniuk, from San Jose State University, found a series of long depressions in the desert along the Mission Creek strand in the Little San Bernadino Mountains which were evidence of previous earthquakes.
By dating the soil in these areas her team was able to work out that the last major earthquake was around 295 years ago.
They used these to calculate that the average slip rate of the Mission Creek strand was around 21.6millimeters (nearly an inch) per year.
This was far higher than the Banning strand (2.5mm), meaning that Mission Creek is at far higher risk of witnessing a major tremor.
This could be a positive for LA for several reasons.
Firstly, having several areas of high tension rather than one means that any resulting earthquakes should be spread out over a wider area, rather than concentrated in a small section.
Secondly, the location of the Mission Creek strand suggests an earthquake in that area will see less of the tension ending up in LA.
While the Banning strand is aligned east-west with the San Bernardino Valley, the San Gabriel Valley, and the Los Angeles Basin, Mission Creek has a north-westerly orientation.
This suggests that some of the tremors from a quake would be diverted away from the Los Angeles basing, sparing the city some of the devastation.
Pictured: Colorful minerals are seen on the Pacific Plate side of the San Andreas Fault, where it collides with the North American Plate, in the southwestern section of the Mecca Hills
The San Andreas fault (pictured, near Hesperia) caused the Great 1906 San Francisco earthquake, when a 7.9 magnitude tremor destroyed 90% of the city and killed more than 3,000 people
A study last June found that the risk of a Big One earthquake along the San Andreas fault in the next 12 months was 2.3%, three times higher than previously thought. Pictured is the fault near the city of Mecca
A train crosses tilted layers of rock along the edge of the San Andreas Fault near Hesperia. The amount of infrastructure in the region means any earthquake could cause millions of dollars worth of damage even if it does not hit an urban area
A study last June found that the risk of a Big One earthquake along the San Andreas fault in the next 12 months was 2.3%, three times higher than previously thought.
The Big One is a hypothetical earthquake of magnitude 8 or greater.
Such a tremor could produce devastation to human civilization within about 50-100 miles of the quake zone, especially in urban areas like Palm Springs, Los Angeles and San Francisco.
In 2019, magnitude 6.4 and magnitude 7.1 Ridgecrest earthquakes hit the area, which according to scientists 'were largely unforeseen.'
If a magnitude 7.8 earthquake were to hit San Andreas it would result in more than 1,800 deaths, injure some 5,000 and displaced up to one million people from their homes.
'Nobody should panic,' earthquake specialist Ross Stein told The New York Times.
'But at the same time, the inference that the San Andreas likelihood of rupture has increased should be a reminder that anybody in Los Angeles should ask themselves, 'Am I ready?''
Dramatic land formations caused by collisions between the Pacific and North American plate, which causes the land to crumple like a sheet of paper
Colorful minerals are brought to the surface by this phenomenon, creating incredible landscapes like this one pictured in Mecca Hills
Properties situated directly on top off on the San Andreas Fault are seen on March 31, 2021 in Desert Hot Springs, California
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