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The magnitude 4.8 Tewksbury earthquake surprised millions of people on the U.S. East Coast who felt the shaking from this largest instrumentally recorded earthquake in New Jersey since 1900.

But researchers noted something else unusual about the earthquake: why did so many people 40 miles away in New York City report strong shaking, while damage near the earthquake's epicenter appeared minimal?

In a paper published in The Seismic Record, YoungHee Kim of Seoul National University and colleagues show how the earthquake's rupture direction may have affected who felt the strongest shaking on 5 April.

Kim and her colleague and co-author Won-Young Kim of Lamont-Doherty Earth Observatory of Columbia University became curious about the strange pattern of shaking after visiting the epicenter area of the earthquake just eight hours after the mainshock.

"We expected some property damage—chimneys knocked down, walls cracked or plaster fallen to the ground—but there were no obvious signs of property damage," the researchers said in an email. "Police officers within a couple of kilometers from the reported epicenter calmly talked about the shaking from the main shock. It was a surprising response by the people and houses for a magnitude 4.8 earthquake in the region."

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