Why earthquakes are felt farther on the East Coast than the West. It's all about the rocks.

Rocks are harder on the East Coast, said USGS seismologist Paul Earle, which makes the seismic waves travel further before they dissipate.

• East Coasters flooded social media with reactions to Friday's earthquake. 
• There's a reason East Coast earthquakes travel further than their West Coast counterparts.
• The rocks are harder, which causes the seismic waves to travel greater distances.

New Yorkers had a lot of feelings about the 4.8-magnitude earthquake that rocked the East Coast Friday morning, with a litany of jokes and memes flooding social media.

Millions felt the quake, United States Geological Survey (USGS) seismologist Paul Earle said in a press briefing Friday, and it also brought air travel to a temporary halt.

But even if earthquakes are de rigeur for West Coasters — some of whom shrugged off the event — the USGS said Friday that there's actually a scientific reason so many East Coasters may have been freaking out.

Earthquakes on the East Coast are experienced much further from their epicenters, according to experts — and it all boils down to differing types of rocks on either side of the country.

Why East Coast quakes are felt farther

Seismic waves can travel much farther through the Eastern type of rock — which is old, cold, and dense — before they decay and dissipate.

"Earthquakes on the East Coast are felt much further — four or five times further than a similar-sized earthquake on the West Coast," Earle said at a press briefing. "The rock is harder, and the seismic waves travel further before they attenuate. And so you're gonna have a lot more people feeling this earthquake than you would a similar-sized earthquake in California."

Veronica Cedillos, the president of GeoHazards International, previously discussed this distinction with Business Insider.

"The earthquake waves — seismic waves — can actually travel much further" on the East Coast, she said. "As opposed to the West Coast, where those seismic waves, actually that energy is absorbed much quicker."

Basically, on the East Coast, seismic waves "can travel a long distance without fading away," Lingsen Meng, associate professor of geophysics at UCLA, told Business Insider.

West Coast quakes are often much deeper

The types of earthquakes that occur on the East and West coasts are also different.

They originate at different depths, which affects how far the waves travel, Ben Fernando, a post-doctoral fellow studying seismology at Johns Hopkins, told BI.

The strongest quakes on the West Coast are usually related to subduction in the tectonic plates — where the Pacific plate is being sucked under the North American plate. That means the earthquakes occur very deep underground, Fernando said.

On the East Coast, however, there's no active subduction.

"It's a very different geological setting," Fernando said.

East Coast quakes tend to be much more shallow. This one was only 3 miles deep, USGS said Friday.

Deeper, West Coast-style quakes usually aren't felt as widely, because the waves have to travel further to the surface.

Still, earthquakes are a rarity in the Tri-state area. Friday's quake had an epicenter 30 miles west of Newark, per the USGS, with people reporting effects from Philadelphia to Boston.

It was the largest recorded earthquake in New Jersey in nearly 250 years. In 2011, a 5.9 magnitude earthquake hit Virginia — marking the last major rattler to hit the East Coast.