At around 10:30 a.m. local time on Friday morning, a magnitude 4.8 earthquake struck approximately three miles below Whitehouse Station, New Jersey. Although it was nowhere near as large as the West Coast quake, the quake's waves traveled hundreds of miles, hitting nearby New York City as well as Philadelphia, Boston, and Washington, D.C. The U.S. Geological Survey is urging the region to prepare for smaller aftershocks.
It was a shock to a region not used to earthquakes. It turns out that its far-reaching effects are not exotic, but rather a byproduct of the East Coast's unique geology, including ancient fault lines and rock formations.
“Earthquakes in this region are unusual, but not unexpected,” Paul Earle, a seismologist with the USGS National Earthquake Information Center, said at a press conference Friday. “Earthquakes on the East Coast are felt much further away than similar earthquakes on the West Coast, four to five times further away.”
For example, back in 2011, people felt the impact of a magnitude 5.8 earthquake up to 600 miles away in Virginia, but a few years later a magnitude 6.8 earthquake in Napa, California, had twice that energy. It was generated, but the distance was less than half. Given that the East Coast is much more densely populated than the West Coast, many people in a much larger area will experience at least a little shaking, even if the magnitude is much smaller than an earthquake like the Loma Prieta earthquake. You will feel it. It devastated the Bay Area in 1989.
The crowded East Coast population can also be blamed on the geology beneath their feet. On the West Coast, vast networks of faults are constantly popping up along active plate boundaries, shocking the entire landscape. “New faults are forming, and old faults are being strained and ruptured in large earthquakes,” said Folarin Kolawole, a structural geologist at Columbia University.
However, when an earthquake occurs on a particular fault, there are adjacent faults that spread the energy. Basically, because there are so many faults along the active plates in the western United States, there are a lot of channels, like underground shock absorbers, to absorb seismic energy.
The USGS has not yet identified the exact fault that caused today's quake, but the quake occurred in an area where the fault system is more static than on the West Coast. An inactive fault somewhere in New Jersey's Ramapo fault system appears to have reactivated Friday morning.
The relative stability of the east coast fault system is due to its geological age. Its rocks were formed hundreds of millions of years earlier than those on the West Coast. Geologically speaking, the East Coast is full of quiet old men, while the West Coast is full of mischievous teenagers.
“The East Coast doesn't have that kind of tectonic complexity,” says Gregory Mountain, a geophysicist at Rutgers University. “Having existed in the geological past, hundreds of millions of years ago, things have been pretty solidified, you could call it that, stable. So on the East Coast, seismic energy is It could actually travel much farther and lose less energy over distance.”
