Expert reveals the devastation that would be unleashed if a Taiwan-style 7.4-magnitude earthquake hit NYC - after East Coast was rattled by a 'baby quake'

Friday morning's earthquake could serve as a wake-up call that the east coast of the US is not immune to quakes normally associated with the west coast, experts say.

Residents of New York, New Jersey, and surrounding areas felt the effects of the 4.8 quake Friday morning. Desks shook, pets got scared, and several minutes later, phones blared with an emergency notification.

Soon after, business returned to usual, and the effects seem to have been minimal. But what if it had been worse? What if this quake had been the same magnitude as the one that rocked Taiwan on Wednesday?

The island nation experienced a 7.4-magnitude earthquake this week, killing 10 people, injuring more than 900, and stranding hundreds more in remote locations around the mountainous country.

Some of the effects of such a quake in New York City could include collapsed buildings, broken water pipes, and damaged roads and subways.

Older brick buildings would be the first to go, as could stone-built major city structures like the New York Public Library the American Museum of Natural History, and other museums and government buildings. 

A death count is hard to estimate, but an earthquake hitting in the daytime would find Manhattan's 1.6 million-person population swollen by four to 10 times with commuting workers, depending on the neighborhood - meaning millions of people at risk of building collapses.

Manhattan's 772,000 households could be without water if water mains break, and people could be without clean running water for days or weeks. With emergency vehicles and evacuees clogging roads, bringing in fresh supplies would take a long time, too.

Subway service, too, could take weeks or months to restore, as the aging system is under strain simply from commuters.

New York City is uniquely prepared for power grid attacks or terrorist attacks, but not earthquakes. 

In Taiwan, dozens of people are still missing as rescue efforts continue apace. 

In the unlikely event that an earthquake of that strength hit New York City, the devastation would likely be significant, according to Dr. Bret Bennington, professor of geology, environment, and sustainability at Hofstra University.

'Buildings that were not built to withstand shaking would would suffer damage and possibly collapse,' he told DailyMail.com

Transportation systems like roads and subways could be damaged, too. This would hinder evacuation and rescue efforts.

And with such a high density of tall buildings that were not built to withstand earthquakes, it is likely that many people would be trapped in damaged buildings or killed when the buildings went down.

'In a city like New York City, the newer buildings, the modern skyscrapers, they're built to move,' said Bennington. 

'They can take a certain amount of swaying motion, because of the wind.'

But many older buildings were not built that way.

The Empire State Building, the Chrysler Building, the Woolworth Building and other old skyscrapers were not built with flexibility in mind.

Newer skyscrapers, even skinny ones, are made to sway in the wind so they would probably survive an earthquake, Bennington said. 

Brick, he explained, is very strong - unless it starts to bend.

'It's brittle. It breaks. So a very powerful earthquake would produce a lot of building facade collapses, ruptured water mains, that kind of thing,' he said.

This stands in stark contrast to Taiwan, where structures are made to stand during quakes - or at least fall in a controlled way. 

As has been the case in other urban earthquakes, the aftermath of building collapses could bring structure fires, too.

And even if New York City's narrow streets were not damaged, they could become a deadly chokepoint for assistance and escape.

Already snarled with traffic on normal days, they could be nearly impossible for emergency vehicles and evacuees to navigate amidst such a natural disaster.

So, how likely is it that such a quake could hit the northeast?

The Richter scale is a logarithmic scale, meaning that each number it goes up is 10 times stronger.

So a 7.4 quake is almost 1,000 times stronger than a 4.8.

'It's not impossible that we would have a magnitude seven earthquake in the New York metropolitan area, it's just highly unlikely,' Bennington said.

Friday's earthquake originated from the Ramapo Fault, Bennet said.

'It forms a significant boundary between two kind of different landscapes in northern New Jersey,' he explained. 'South of the fault, you have relative lowlands, and north of the fault, you have mountains.'

This major fault runs across New Jersey, into New York, and across the Hudson River north of New York City.

The Ramapo Fault is what's called a 'normal fault' where two tectonic plates meet at a roughly vertical angle.

At a normal fault, one plate's edge is slipping down and away from the other as the two plates slowly move away from each other.

There has been movement at this fault for potentially 200 million years, said Bennington.

'Most of that movement probably happened way back in the Mesozoic, but the fault is still there, and rock can still move along that fault,' he said.

The North American Plate may be moving west away from the mid-ocean ridge at about the same rate as our fingernails grow, but it's not smooth. 

Once enough tension has accumulated from the slow movement at the plate boundary, it releases in the form of an earthquake. 

Earthquakes occur when the two plates on either side of a fault suddenly move, expelling the built-up energy from the plates pressing against each other.

At the Ramapo Fault, the likelihood of a major quake is rather low, said Bennington.

On the west coast, better known for earthquakes, the western edge of the North American Plate is bumping up against the Pacific Ocean floor, 'and there really isn't anywhere to go,' he said.

Couple that with the Pacific Plate moving up against the North American Plate, and the west coast has more motion and strain energy, and therefore bigger quakes.

But at the Ramapo Fault, there is room for the rock to move when it builds up too much tension, meaning that a strong quake is less likely.

Nor is a tsunami likely, he said.

For that to happen, there would need to be movement of a plate on the seafloor, but the seafloor near the east coast is firmly attached to the North American Plate - the same plate New York sits on.

And at the Mid-Ocean Ridge in the Atlantic Ocean, the plates are spreading apart - not the conditions that would create a tsunami. 

You never know what could happen, though, Bennington acknowledged.

In 1886 a 7-magnitude earthquake hit Charleston, South Carolina, causing cratering and fissuring, and damaging about 50 miles of railroad tracks. 

It is not possible to forecast an earthquake or warn people that one is about to happen.

They just happen.

So even though such an event is unlikely, if it occurred there would be no warning.