In Southern California, the landscape is fractured in the shape of an enormous letter Z. The top arm is made up of a winding series of cracks that were responsible for q uakes that rattled the city of Ridgecrest last year. The diagonal section is an ancient fault called Garlock that runs to the west. And along the bottom sits the mighty San Andreas.
Earthquakes along this lengthy fault, which runs more than 800 miles through California, are an ever-looming concern—and a new study suggests that in the next year, a large quake near the bustling city of Los Angeles could be three to five times more likely than previously thought. The research, published in the Bulletin of the Seismological Society of America, found that the 2019 Ridgecrest earthquakes made a future quake along the nearby Garlock fault more likely. If a big enough quake hits Garlock, it could trigger the San Andreas fault as well—a series of events that the researchers estimate has about a 1 in 87 probability of occurring within the next year.
However, the overall probability of such an event remains low. The research team estimates that there is a 2.3 percent chance of a magnitude 7.7 earthquake occurring on the Garlock fault in the next year, and a 1.15 percent chance of a similar quake hitting San Andreas.
“So, the sky is not falling,” says study co-author Ross Stein, CEO of Temblor, Inc., a company that assesses risks from hazards such as earthquakes. “But it...