About five minutes after Fran Mathews went to bed, she heard a boom and felt her house in northern Harford County shudder.
"I was afraid enough to see if the furnace had blown up," said Mathews, 61.
What rattled Mathews and others in northern Harford County yesterday was a minor earthquake at 12:04 a.m. in Lancaster County, Pa.
The 3.3-magnitude quake was centered in the Salunga-Landisville area, about 40 miles north of the Pennsylvania-Maryland line, according to the U.S. Geological Survey.
Lorenz Mannino was watching television at his home near Whiteford at the time. He thought the sound that made his house "shake a little" was either a windstorm or a truck roaring by.
"It was weird," said Mannino, who owns a pizza shop.
More than 1,000 residents of Lancaster County called the county 911 center after feeling the tremors, according to the emergency dispatch center. No injuries were reported.
The Harford County emergency operations center received about a dozen calls, dispatcher Brandon Ruble said.
The earthquake was the seventh minor one to hit Pennsylvania since early October, according to USGS data. The tremors were centered within 23 miles of yesterday's earthquake.
The Maryland Emergency Management Agency noted the quake in its incident log, but it didn't receive any requests for help, chief of staff Edward Hopkins said.
Hopkins, who lives in Bel Air, said he was unaware of what had happened until getting up yesterday morning.
"Coming off the Christmas holiday with the kids, by the time I got to bed, I didn't hear a thing," Hopkins said.
Mathews, a retired athletic director at North Harford High School, said that after hearing the loud sound that shook her house, she checked on the furnace and then looked out the window to find out if there had been an explosion in her neighborhood.
A Whiteford resident since 1981, Mathews said it was the first time she had felt an earthquake. "It was strange, but there was nothing else after that," she said.
The Allentown Morning Call contributed to this article.