A major earthquake of magnitude 7.8 shook the Seattle area roughly 1,100 years ago when a succession of buried fissures burst at the same time, according to a new study. Something similar could happen again, with disastrous consequences.
Earthquakes occur when tectonic plates become entangled at their edges owing to friction and the stress on the edge overcomes the friction. Such action releases energy in the form of waves that flow through the earth’s crust, causing us to tremble.
Other fault lines and accompanying folds in the United States include the Seattle fault. It stretches along Seattle’s northern boundary and up to the Olympic Peninsula.
The most recent study, published on Wednesday (Sep 27) in the journal Science Advances, examined an earth-shifting event that occurred more than a millennium ago in the Puget Sound region, which includes Seattle and Tacoma.
According to the study, the quake caused landslides, upliftment of fault fragments, and a minor tsunami, which drowned and buried many local trees throughout an area of 193 square miles.
Seattle’s ongoing earthquake threat highlights the urgency for preparedness
According to some reports, the region is a structurally complex, seismically active trough located between the Coast Range and the Cascade volcanic arc. Deep quakes of magnitude greater than six happened in the indicated region in 1909, 1939, 1946, 1949, 1965, and 2001, according to the Seattle municipality.
According to the government website, earthquakes are the most significant threat to Seattle, and unlike other potentially catastrophic risks, Seattle has experienced and will suffer powerful earthquakes.
As the latest report examines the multifault earthquake potential for the Seattle metropolitan region, scientists urge authorities to make proper efforts to limit the repercussions.
According to the study, researchers employed dendrochronological dating and a cosmogenic radiation pulse to restrict the death dates of earthquake-killed trees along two neighboring fault zones near Seattle, Washington between the 923 and 924 CE growing seasons.
“Our narrow constraints conclusively show linked rupturing that occurred either as a single composite earthquake of estimated magnitude 7.8 or as a closely spaced double earthquake sequence with estimated magnitudes of 7.5 and 7.3,” the authors in the study said.
Tree dating unveils past earthquake cluster
Divers were recruited by researchers to bring a tree sample gathered from an earthquake-damaged tree in Washington’s Price Lake to the surface. The team used radiocarbon and tree-ring dating to determine when the trees perished.
They discovered that the trees died between 923 and 924 AD, over a six-month period. It implies that the earthquakes in the Puget Sound region occurred in a short period of time.
According to the press release, the researchers assessed that a single multi-fault earthquake with a magnitude of roughly 7.8 may have occurred, but two earthquakes during that six-month period would have each exceeded 7.3.
According to the study, these situations, which are not included in existing hazard models, raise the maximum earthquake size required for seismic preparedness and engineering design within the Puget Sound region of >4 million residents.
