Geologists have found a link between the two largest fault systems on the U.S. West Coast: earthquakes along them may occur just minutes or hours apart, infohub.kz reports.
The two most closely studied fault systems on North America's West Coast may be more connected than previously thought. According to a new study, the Cascadia subduction zone and the San Andreas fault can synchronize. That means a powerful quake on one of them could trigger seismic activity on the other.
A research team led by Chris Goldfinger, a marine geologist at Oregon State University, examined seabed sediments covering roughly 3,100 years of geological history. By analyzing turbidites — layers of sediment left by underwater landslides caused by strong earthquakes — the scientists found unusual paired structures known as "doublets." In these layers, fine silt from a Cascadia earthquake was overlain by coarse sand from a San Andreas rupture.
The study found that over the past 1,500 years there were at least three instances when Cascadia and the northern part of San Andreas ruptured within minutes to hours of each other. The most recent such episode was recorded around 1700. The key samples were obtained by chance back in 1999 during a marine expedition near Cape Mendocino in California, where the two geological systems converge.
The findings point to the need to revise disaster response plans. If both faults were to rupture at the same time, the region's largest metropolitan areas, including San Francisco, Portland, Seattle and Vancouver, would simultaneously find themselves in the emergency zone, putting unprecedented strain on rescue services.