- East Coast residents flooded social media with reactions to Friday’s earthquake.
- There’s a reason why East Coast earthquakes propagate further than their West Coast counterparts.
- Rocks are harder, so seismic waves travel greater distances.
New Yorkers were deeply moved by the 4.8 magnitude earthquake that shook the East Coast Friday morning, with a litany of jokes and memes flooding social media.
Millions of people felt the quake, Paul Earle, a seismologist with the United States Geological Survey (USGS), said at a news briefing Friday, and the quake also led to the temporary shutdown of air travel.
But even if earthquakes are de rigeur for West Coasters – some of whom raise the shoulders the event — the USGS said Friday that there was actually a scientific reason why many East Coast residents may have panicked.
Earthquakes on the East Coast are felt much farther from their epicenters, experts say — and it all comes down to different rock types on each side of the country.
Why East Coast earthquakes are felt farther away
Seismic waves can travel much further through oriental-type rocks – which are old, cold and dense – before disintegrating and dissipating.
“Earthquakes on the East Coast are felt much farther away, four or five times farther away than an earthquake of the same magnitude on the West Coast,” Earle said during a press briefing. “The rock is harder and the seismic waves travel farther before attenuating. And so many more people will feel this earthquake than a similar sized earthquake in California.”
Veronica Cedillos, president of GeoHazards International, previously discussed this distinction with Business Insider.
“Seismic waves – seismic waves – can actually propagate much further” on the East Coast, she said. “Unlike the West Coast, where these seismic waves occur, this energy is absorbed much more quickly.”
Basically, on the East Coast, seismic waves “can travel a long distance without disappearing,” Lingsen Meng, an associate professor of geophysics at UCLA, told Business Insider.
West Coast earthquakes are often much deeper
The types of earthquakes that occur on the east and west coasts are also different.
They come from different depths, which affects how far the waves travel, Ben Fernando, a postdoctoral researcher studying seismology at Johns Hopkins, told BI.
The strongest earthquakes on the West Coast are generally linked to tectonic plate subduction, where the Pacific plate is sucked under the North American plate. This means that earthquakes occur very deep underground, Fernando explained.
On the East Coast, however, there is no active subduction.
“It’s a very different geological environment,” Fernando said.
Earthquakes on the East Coast tend to be much more shallow. This one was only 3 miles deep, the USGS said Friday.
Deeper earthquakes, similar to those on the West Coast, are generally not felt as widely because the waves have to travel farther toward the surface.
Still, earthquakes are rare in the tri-state area. Friday’s quake had an epicenter 30 miles west of Newark, according to the USGS, and people reported effects from Philadelphia to Boston.
It was the largest earthquake recorded in New Jersey in nearly 250 years. In 2011, a 5.9 magnitude earthquake struck Virginia, marking the last major earthquake to hit the East Coast.
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