The findings from new research, led by University of Arizona dendrochronologist Bryan Black, could have implications for seismic preparedness measures in the region.
In February, a 7.8-magnitude earthquake shook the Turkey-Syria border, followed by one nearly as large nine hours later. Shallow faults less than 18 miles beneath the surface buckled and ruptured, causing violent focused quakes that leveled thousands of buildings and killed tens of thousands.
Similar shallow faults ruptured about 1,000 years ago in the Puget Lowlands in western Washington, according to new University of Arizona-led research. Tree rings helped pinpoint that the seismic event occurred in late A.D. 923 or early 924. Their findings mean that a repeat event has the potential to again shake the region that is now home to over 4 million people, including Seattle, Tacoma and Olympia. The results were published in the journal Science Advances.
The ancient quake was either the result of all the shallow faults in the region rupturing together to produce an estimated 7.8-magnitude earthquake or – like in Turkey and Syria – twin quakes that occurred back-to-back with estimated magnitudes of 7.5 and 7.3, researchers found. Shallow faults typically result in more violent and focused shaking than earthquakes generated from other geological configurations.
Read more at University of Arizona
Image: Price Lake, in the eastern Olympic Mountains, formed when the Saddle Mountain fault impounded a stream and flooded the forest. Lead author Bryan Black and his team of divers collected the samples using an underwater hydraulic chainsaw. (Credit: Bryan Black)