At a general store in New Jersey, near the epicenter of the earthquake, the sound was so loud that the staff thought a truck had crashed into the building.

Five miles away, at some riding stables, the ground shook so forcefully that it sent three horses galloping around the ring.

Within hours, a custom T-shirt shop in Manhattan was already selling a souvenir: a shirt emblazoned with, “I Survived The N.Y.C. Earthquake, April 5th, 2024.”

For most of the millions of people who felt the magnitude-4.8 earthquake that sent tremors from Philadelphia to Boston on Friday morning, it was a harmless novelty in a part of the country unaccustomed to seismic shaking.

But the rattling shook buildings in New York City and drove startled residents into the streets. Aftershocks continued throughout the day Friday, including one that measured 4.0 just before 6 p.m. and that was felt widely across New York and New Jersey.

Aftershocks would likely “continue for several days and even a week,” said Kishor S. Jaiswal, a research structural engineer with the United States Geological Survey. There is also a small chance that an earthquake of similar or even larger magnitude could occur during such a sequence, he said.