Facebook and Twitter proved to be a key source of information during and after Tuesday’s East Coast earthquake, as cellphone networks struggled with congestion from an overwhelming number of callers.

The earthquake hit at 1:51 p.m., according to the U.S. Geological Survey, and just four minutes later, Facebook said the term “earthquake” appeared in the status updates of 3 million users.

Twitter lit up with questions, on-the-ground descriptions of the 5.8 magnitude quake and messages to family and friends.

Within a minute of the quake, there were more than 40,000 earthquake-related Tweets. The micro-blogging site said it hit about 5,500 Tweets per second on the quake, which is more than Osama Bin Laden’s death in May and on par with tweets related to the Japanese quake in March.

Some reported on Twitter and Facebook that they learned about the quake on the Web sites before they felt it.

“Earthquake” was the number one trending word on Twitter across the East Coast Tuesday, including in Richmond, the District, Raleigh, Boston, Providence, New York City, Philadelphia, Baltimore and Pittsburgh.

And here’s our story on the disruption to cellphone service.