Understanding Earthquake Differences: Why Eastern US Quakes Stand Apart

DEBARYLIFE – Five states, including New Jersey, were hit by a 4.8-magnitude earthquake early Friday morning. The ground and people on the East Coast were shaking.

The Americas Geological Survey (USGS) says the quake happened at 10:23 a.m., about 5 miles north of Whitehouse Station, New Jersey. New Yorkers felt their floors and chairs shake because the epicenter of the earthquake was about 45 miles away.

An earthquake was felt by people from Norfolk, Virginia, to Maine. Ground ripples were felt in parts of Connecticut, Pennsylvania, and Massachusetts.

In contrast to the West Coast, where California “gets two or three earthquakes large enough to cause moderate damage to structures (magnitude 5.5 and higher)” every year, the East Coast doesn’t have many earthquakes.

That the East Coast should still be worried about earthquakes. While earthquakes happen less often on the West Coast, they have happened in every state east of the Mississippi River, according to the USGS. An office of the federal government that studies the country’s landscape, natural resources, and natural hazards said that some of the quakes were big enough to damage almost all southeast states.

“Since colonial times people in the New York – Philadelphia – Wilmington urban corridor have felt small earthquakes and suffered damage from infrequent larger ones,” as per the USGS. “Moderately damaging earthquakes strike somewhere in the urban corridor roughly twice a century, and smaller earthquakes are felt roughly every 2-3 years.”

“The surgeon kind of froze,” reports a man who was getting a vasectomy on Friday during an earthquake.

An earthquake on the East Coast generally causes “higher-frequency shaking (fast back-and-forth motion) compared to similar events in the West,” according to the USGS.

Usually, shorter buildings are more likely to be damaged when there is faster shaking, while taller structures are more likely to be damaged when there is slower shaking, according to the agency.

SEE MORE: New Jersey Earthquake Sends Aftershock Tremors Through East Coast Communities

“Many of the older structures in the East, such as buildings and bridges built before the 1970s, were not designed to endure earthquakes and therefore may not fare well,” the USGS noted.

The East Coast is making progress in updating older buildings and building new ones that meet newer design standards, according to the USGS. These changes are more common on the West Coast, where older buildings are updated and new buildings are often “designed to withstand strong shaking,” the agency said.

Why do West Coast earthquakes happen more often?

It has more earthquakes in the western U.S. because it “lies along the boundaries of major tectonic plates that make up the Earth’s crust—the North American Plate and the ocean plates to the West,” according to the USGS.

“These plates are moving against each other, breaking up the crust along many faults like the San Andreas Fault,” a report says. “Faults in the East are less active and lie entirely within the North American Plate.”They have a harder time figuring out how often and how big earthquakes are on the East Coast because of the geography of the area and the “relatively sparse history of earthquakes to study,” according to the USGS.

“Eastern earthquakes are more of a mystery because they do not take place at a plate boundary where most other earthquakes originate,” said the agency. “Scientists do not fully understand the state of stress within tectonic plates, and they are studying how stresses accumulate and evolve and how earthquakes are triggered.”

Weakly detectable cracks on the East Coast, according to the USGS.

SEE MORE: The Biggest Earthquake in Pennsylvania’s History Shut Down the State

An additional problem for experts is finding the active faults on the East Coast.

“Most faults have not had major earthquakes or movement in the past few million years, and the faults that are active may only have earthquakes every few thousand or tens of thousands of years,” as per the USGS. “Any evidence of past earthquakes on the land’s surface in the eastern U.S. is often obscured by vegetation or is more subdued because of erosion.”

To the contrary, the West Coast has more active faults and places with little vegetation, so earthquakes can leave clear marks that help scientists figure out the history, size, and effects, according to the government agency.

What effect does fracking have on US earthquakes?

The ones that do happen “have generally been small,” according to the American Institute of Physics news service, and North American fracking isn’t known for causing massive earthquakes.

A lot of the recent earthquakes in the central U.S. are caused by getting rid of waste fluids, which are a result of oil production, the USGS said.

“Wastewater disposal wells typically operate for longer durations and inject much more fluid than is injected during the hydraulic fracturing process, making them more likely to induce earthquakes,” a government agency said.

The four-magnitude 2018 Texas earthquake was the biggest one caused by fracking in the United States, according to the USGS.