New research has discovered a subterranean ‘structure’ beneath the San Andreas fault line which could trigger a massive quake – dubbed the “big one”.
The 800-mile long fault line is the meeting point of two huge tectonic plates: the Pacific Plate and the North American Plate.
The boundary is a hotbed of earthquake activity in the United States, lying along the quake hotspot known as the Ring of Fire which circles the Pacific Ocean.
But a team of experts now believe they have located the specific section where the next major tremor will hit.
The 15.5-mile-long formation, dubbed the ‘Durmid Ladder’, sits at the southern end of the San Andreas fault and geologist Susanne Jänecke believes the area could be ground zero for a massive quake.
Dr Jänecke, a professor at Utah State University, and her team carried out a detailed study of the area and discovered the highly faulted, ladder-like structure.
The research revealed the Durmid Ladder extends from the main line of the San Andreas fault to a newly-identified fault zone known as East Shoreline.
In the study, which was published in the peer-reviewed journal Lithosphere, she said: “We now have critical evidence about the possible nucleation site of the next major earthquake on the San Andreas Fault.
“That possible nucleation site was thought to be a small area near Bombay Beach, California, but our work suggests there may be an additional, longer ‘fuse’ south of the Durmid Ladder within the 37-mile-long Brawley Seismic zone.”
The research also predicted there is a 75 percent chance of a magnitude seven or larger tremor hitting both the north and south regions of the state within the next 30 years.
But Dr Jänecke acknowledged it is not clear how the Durmid Ladder interacted with past earthquakes along the San Andreas fault.
Because of this uncertainty, predicting the behavior of future tremors is made much harder, the geologist said.
Dr Walter Mooney, from the US Geological Survey, said the Durmid Ladder could trigger a huge earthquake because of its unique shape.
Speaking to San Francisco-based television station KRON4, he said: “If you have a ladder and you break a rung or a step, then the ladder begins to deform, and if you break another rung, well I wouldn’t want to be on that ladder because the whole thing, both sides could go.
“We would be very concerned if we begin to see movement on that ladder structure because it could trigger or influence or encourage other associated faults to move and what we’re really afraid of is a big one, a magnitude eight in Southern California.”