Evidence Of Massive Earthquake In US 1,100 Years Ago Suggests It Could Happen Again


Kay Smythe News and Commentary Writer
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A study published Wednesday details how an enormous 7.8 magnitude earthquake struck the Puget Sound region 1,100 years ago, and it could definitely strike again.

Using dendrochronological records of earthquake-killed trees, the study researchers narrowed the date of the last major earthquake to between the 923 and 924 A.D. growing seasons. It’s unclear whether the quake hit as one major 7.8 or higher shake, or if it was a series of earthquakes estimated between a 7.5 to 7.3 in magnitude, that killed the trees.

But it seems most likely that at least two major earthquakes occurred in quick succession along with the Seattle Fault Zone (SFZ) and the Saddle Mountain Fault Zone (SMFZ). Current hazard models do not take simultaneous faulting into account as a scientific reality, leaving some 4 million people living in Seattle, Tacoma, and Olympia at significant risk of the next big one.

Earthquakes like this are extremely rare, but they do happen. And simultaneous and rapid ruptures or extremely high magnitude events aren’t just limited to this one region of Washington State. (RELATED: Family’s Only Survivor Is Baby Who Was Born While Mother Was Trapped Under Rubble From Earthquake)

An enormous fault line lies just offshore, known as the Cascadia Subduction Zone fault (CSZ), LiveScience reported. The 620 mile (1,000 kilometer) fault stretches from Northern California to Vancouver Island, and is capable of producing earthquakes of a magnitude 9, which would literally devastate the entire West Coast as it did around the year 1700.

The last time this fault was seriously active, residents of the region were hit with landslides, collapsed homes, and a tsunami destroyed an entire village, killing every single resident, Earthquakes Canada reported. Some 13 massive earthquakes have occurred along the fault in the last 6,000 years. We know one will happen again, we just don’t know when.

And when it does hit, the National Oceanic and Atmospheric Administration estimates the shaking will last anywhere from four to six minutes, and a tsunami will hit the region within 15 to 30 minutes. To put in perspective, the Northridge earthquake in 1994 only lasted 10 or 20 seconds at most, Britannic noted.