- A magnitude 7.8 earthquake shook the Seattle region 1,100 years ago
- Experts discovered that it came from two fault lines that ruptured at the same time
- READ MORE: Seattle could be engulfed by a TSUNAMI with waves up to 42ft
A massive 7.8-magnitude “megaquake” rocked the Seattle area 1,100 years ago when two fault lines ruptured at the same time – and experts fear it could happen again.
The faults are located in Puget Sound, which includes Seattle, Tacoma and Olympia, and have ruptured in the past, but the century-old quake was 30 times more powerful than current warning signals suggest these fault zones are possible.
A team of scientists led by the University of Arizona discovered the natural disaster and determined that it caused landslides and a local tsunami that would be catastrophic if it hit the region where more than four million people live today.
A 2005 scenario showed that even a magnitude 6.7 earthquake would kill more than 1,600 people, destroy nearly 10,000 buildings and cause total economic losses of $50 billion.
A team of scientists led by the University of Arizona discovered the natural disaster and determined that it caused landslides and a local tsunami that would be catastrophic if it hit the region where more than four million people live today.
The faults in question are the Seattle Fault Zone (SFZ), located beneath and around the city, and another from the Saddle Mountain Fault Zone (SMFZ) in southwestern Washington.
Researchers recovered fossilized Douglas fir trees from six Puget Sound sites associated with the Seattle and Saddle Mountain fault zones, which were believed to have been destroyed by seismic activity.
The team then measured the radiocarbon concentrations in the wood, which allowed them to determine the year each tree fell from its roots.
All the trees were killed within six months, between 923 and 924.
These findings explain two scenarios that could have happened.
The faults are in Puget Sound, which includes Seattle, Tacoma and Olympia, and have ruptured in the past, but the old quake was 30 times more powerful than current warning signals suggest is possible from the fault zones.
In these early cases, the two faults ruptured as two earthquakes, hours to months apart: the Seattle fault zone had a magnitude 7.5 earthquake, and the Saddle Mountain fault zone had a magnitude 7.3 earthquake.
“The second possibility is a single, larger, multi-fault earthquake rupturing both the Seattle and Saddle Mountain fault zones with an estimated average magnitude of 7.8,” the study reads.
The team noted in the study that ruptures had occurred simultaneously elsewhere in our modern world, including a magnitude 7.9 earthquake in 2001 in southern Alaska, a magnitude 7.3 earthquake in 1992 in southern Alaska California and a magnitude 7.8 earthquake that struck New Zealand in 2016. more than 20 different errors.
In the case of Puget Sound, scientists think the two faults may be kinematically linked.
A 2022 study by researchers at the Washington State Department of Natural Resources also looked at a megaquake that hit Seattle, but it only had a magnitude of 7.5.
The model showed that waves of 12 meters high would engulf the city within three minutes.
The 40-foot waves would swirl around the landmark Seattle Great Wheel and reach inland as far as Lumen Field stadium, home of the Seattle Seahawks, and T-Mobile Park, where the Seattle Mariners baseball team plays.
Thirty miles south of downtown, waves in Tacoma Harbor could reach as much as three miles inland.