San Andreas Fault: Extremely Deep Originating Earthquakes Making Scientists Nervous
A NEW study has revealed that earthquakes in California are originating from much deeper underground than it was thought, meaning that they will be even more devastating than previously feared.
Californians are currently on a knife-edge as experts believe that they could be close to a devastating earthquake when the San Andreas fault finally gives.
Seismologists thought that powerful earthquakes had stemmed from 12 to 15 miles beneath the surface, but new research suggests that they can come from more than 15 miles underground – into the Earth’s mantle.
From analysing data collected by state-of-the-art sensors over the last six months at California’s Long Beach – where a 6.4 magnitude quake struck in 1933 – they found that the fault that it sits on top of, the Newport-Inglewood fault, extended into the mantle.
The team believe that if a tremor occurs near to the surface, it could rattle down to the bottom of the fault and cause much more damage than previously thought.
A California Institute of Technology (CalTech) seismology professor, Jean Paul Ampuero, said: “That got us thinking – that if earthquakes want to get big, one way of achieving that is by penetrating deep.
“The big question is: If the next, larger earthquake happens, if it manages to penetrate deeper than we think, it may be bigger than we expect.”
The fault lines could reach the Earth’s mantle
The team point to the 8.6 earthquake which hit the Indian Ocean in 2012 which was the largest quake of its kind “that has ever happened” according to Mr Ampuero.
The fault that that huge tremor occurred on was a “strike-slip” fault, which is the same as the Newport-Inglewood and San Andreas fault.
It was impossible to explain at the time how such a huge quake had happened, but now the experts believe that the fault may dig deeper into the mantle, which would explain how it became so powerful.
The study, published in the journal Science, suggests that if this theory does prove to be true, residents of California who reside near to the Newport-Inglewood and San Andreas faults could be in for a much more powerful earthquake than previously forecasted.
SEAN MARTIN – Express
