Tree rings reveal a new kind of earthquake threat to the Pacific Northwest

Wednesday, September 27, 2023

Tree rings reveal a new kind of earthquake threat to the Pacific Northwest

The findings from new research, led by University of Arizona dendrochronologist Bryan Black, could have implications for seismic preparedness measures in the region. Read the UA New story here.

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. Using the natural clocks preserved within the carcasses of trees and aided by a mysterious cosmic explosion that showered Earth in radiation, researchers have fairly precisely pinned down a seismic event in the Puget Sound area to within a six-month period in the 10th century C.E. 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.

Read more in the Seattle Times article, The Science article, and the Scientific America article.