Big Quake Rattles East Coast

A 5.8 earthquake sent jitters through major population centers up and down the east coast of the U.S. yesterday. People from Toronto to Atlanta felt the moderate quake which was centered along the Central Virginia Seismic Zone near Mineral, Virginia.

The east coast doesn’t get major temblors like the west coast. And that’s why many people preparing for the 10th anniversary of the September 11th terror attacks ran from shaking buildings, thought bombs were going off and hoped for the best while thinking the worst.

Close to the epicenter, groceries toppled from store shelves, roofs collapsed and furniture was upset. The quake was very shallow, measuring just two and a half miles deep. And given the solid terrain of the east coast the seismic waves that the quake released reverberated from northeastern Wisconsin to the Gulf coast.

According to seismologists the east coast and west coast produce very different quakes. People on the west coast laughed off the quake in the east because the younger, more plastic rocks along the Pacific Ring of Fire break regularly and release energy in the form of earthquakes. But those quakes don’t radiate very far because the seismic waves quickly run into other faults which absorb the shaking power.

The east coast on the other hand is much older and the rocks are more solid and less pliable. Therefore, a shaker in the east tends to radiate seismic waves much greater distances and the damage while focused near the epicenter can also propagate much further.

After yesterday’s big quake, Washington D.C. which is about 83 miles north of the epicenter evacuated all federal buildings, including the monuments. Part of the Pentagon flooded when a water pipe burst during the quake. The Washington Monument received a new battle scar as a crack formed in the top of the pyramid. And a spire on the National Cathedral came crashing down during the quake.

In New York, fears of a terror attack rattled nerves much more than the actual shaking. But people fled skyscrapers and dashed into the streets waiting for the shaking to stop and someone to explain what was happening.

Dr. Nick Evans is one of few people who understands the complexity of studying earthquakes in Virginia. And he also had the distinction of being on a long distance bike trip in Maine when the quake happened. Connected to the quake through his smartphone, he says that once he found out his home was still standing he went back to his vacation.

He says there is an ancient tectonic plate boundary near Mineral, located in the Central Virginia Seismic Zone. This zone of seismic activity is a place where earthquakes happen somewhat frequently but they are usually too small to cause much commotion.

Dr. Evans, who runs a a science-based well drilling firm says that studying earthquakes in Virginia is a tricky business. For one, he says the deformation of rock takes place below the surface and unlike in California there aren’t any surface ruptures that make it easy to follow the fault.

In Virginia and throughout the east coast, there is just one plate — the North Atlantic tectonic plate. Quakes generally occur when a plate boundary sinks or subducts under another plate and creates friction. When enough pressure builds up the crust suddenly shifts or breaks, causing an earthquake.

Hundreds of miles from any plate boundary, seismologists studying the area think that an ancient fault, though they don’t know which one, triggered Tuesday’s earthquake.

Dr. Evans studied the seismology of Virginia for his doctoral dissertation and says that few geologists look at the area because quakes are not terribly common and the action takes place underground where it is harder to study.

Because the quake was so shallow I called Dr. Evans to see if there could possibly be a man-made reason for the quake. In recent years hydraulic fracturing has become a common technique to reach natural gas pockets buried in the bedrock. Hydrofracking as it is called is also being blamed on several earthquake clusters in Arkansas and other states where the technique is being used.

There is no hydrofracking going on in Virginia right now and only one county about 90 miles from the epicenter has approved the technique though no drilling has begun. Oil and natural gas companies have discovered a massive amount of potential fuel buried in the Marcellus Shale, a rock formation that stretches from New York through Pennsylvania to the edge of Virginia.

According to Steve Johnson who monitors hydraulic fracturing in the area, there is no hydrofraking activity or testing in the area near the epicenter in Mineral, Virginia. He says that the nearest drilling is going on in the Marcellus Shale about 60 miles away.

Dr. Evans says that despite Internet speculation, hydrofracking as the cause of Tuesday’s big quake is a “non-starter.”

He adds that Virginia is full of holes. His company drills water wells all the time though only to a depth of about 300 feet. Gold mining and other mineral extraction is pretty common near the quake’s epicenter. He says there are a lot of holes in the area but none is responsible for the quake that rocked a quiet Tuesday afternoon along the eastern seaboard.

Within minutes of the quake nerves settled as people realized it was just Mother Nature letting off some late summer steam.