The earthquake was the strongest recorded east of the Rocky Mountains since 1944 and the strongest ever recorded in central Virginia’s seismic zone.

“For a geologist, the 2011 earthquake was unequivocally one of the most geologically and historically significant moments in the Commonwealth,” said Virginia state geologist David Spears.

It’s believed that the quake was the most widely felt in the history of the United States with up to one third of the population rocking and rolling on that sunny work day. It was also felt all the way in Canada.

There were dozens of aftershocks, one a 4.5-magnitude, which struck in the middle of the night, startling this reporter out of his slumber.

So why did the earthquake occur? Millions of years ago, the North American and European continents slammed into each other several times creating the Appalachian Mountains, and when they separated the Atlantic Ocean was born. As a result of the continental collisions there are numerous but mostly quiet faults on the East Coast.

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The earthquake occurred in a hot spot for quakes known as the Virginia Seismic Zone, according to Thomas Pratt with the U.S. Geological Survey Geologic Hazards Science Center. “Aftershocks continue today,” Pratt said. “However, they are becoming less numerous.”

It was nOt just humans that were rattled. Our primate cousins at the National Zoo actually sensed it coming, according to a 2011 press release:

The earthquake hit the Great Ape House and Think Tank Exhibit during afternoon feeding time. About five to ten seconds before the quake, many of the apes, including Kyle (an orangutan) and Kojo (a western lowland gorilla), abandoned their food and climbed to the top of the tree-like structure in the exhibit. About three seconds before the quake, Mandara (a gorilla) let out a shriek and collected her baby, Kibibi, and moved to the top of the tree structure as well. Iris (an orangutan) began “belch vocalizing” — an unhappy/upset noise normally reserved for extreme irritation — before the quake and continued this vocalization following the quake.

The memory from that day has not faded, and there are reminders of the event around town. The National Cathedral is still in need of millions of dollars to complete its restoration of gargoyles and other decorations on the exterior of the building.