San Andreas Fault: Next Big Earthquake Location Identified by Geologists

Geologists have identified a new section of California's famous San Andreas Fault (SAF), which could be the site of the region's next major earthquake, according to a study published in the journal Lithosphere.

The seismically active, 15.5-mile-long stretch is buried in silt at the bottom of the Salton Sea—a shallow, salty lake that sits directly on top of the SAF's southern tip. It has been named the "Durmid Ladder" by the researchers from Utah State University (USU), because it consists of two master faults and hundreds of smaller rung-like faults that run perpendicular to these.

This Durmid Ladder measures between 0.6 and 2.5 miles wide and extends from the main part of the SAF along the Salton Sea's northeastern shore, to another newly identified stretch called the East Shoreline Fault Zone (ESF).

"We now have critical evidence about the possible nucleation site of the next major earthquake on the San Andreas Fault," Susanne Jänecke, a geologist from USU, said in a statement.

The researchers identified the new fault section using a combination of high resolution aerial photography, false color imaging and drilling.

They say that future seismic activity in this zone could potentially trigger a cascade of earthquakes that leads to "the Big One"—a massive earthquake of magnitude 8.0 or greater, which is predicted to occur along the SAF and is long overdue. Such a quake would likely prove devastating to the areas surrounding the epicenter.

In 1906, a powerful 7.9 magnitude earthquake caused the deaths of up to 3,000 people and destroyed more than 80 percent of the city of San Francisco in what was one of the worst natural disasters in American history.

Jänecke notes that only the main section of the SAF has been well-studied in the Salton Sea region, and so further research needs to be conducted into the Durmid Ladder and the East Shoreline Fault Zone.

The Lithosphere paper comes in the wake of a study published recently in the journal Nature Geoscience, which found that a phenomenon called "slow earthquakes" could trigger more destructive quakes along the San Andreas Fault.

The study demonstrated that the movement of plates along the central section of the SAF has not been as smooth and steady as previously thought and was instead characterized by small "stick-and-slip" movements—known as slow earthquakes—which release energy over a period of hours to months, rather than seconds to minutes like a typical quake.

While studies such as these can help researchers better understand how and when quakes will occur, they are still very difficult to predict.

Current models suggest that there is around a 75 percent chance of a magnitude 7 or greater earthquake occurring in both Northern and Southern California within the next 30 years, according to researchers from Arizona State University.