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According to Ms. Schwartz, who was working at a building across the street from the World Trade Center site, “there were thousands of people standing around … maybe people were waiting to leave, maybe they were trying to decide if they should go back to work. My feeling is that no one really knew what they should do.”

New Jersey Web developer Steve Greydanus said he was on a conference call with colleagues in Baltimore and Sacramento, Calif., when the quake hit.

“My co-worker Felicia in Baltimore felt it for 30 seconds before we did up here. And she sounded pretty panicked,” Mr. Greydanus said, going on to note ironically that the Sacramento colleague had never been in an earthquake.

According to Mr. Greydanus, another colleague at his office in Lyndhurst, N.J., whom he described as apparently having animallike senses, said almost simultaneously that she was “getting that light-headed feeling like I did before that last quake.”

The tremor did have some immediate — albeit temporary — impact in a very jumpy part of New York: Wall Street. The Dow Jones industrial average, which was in the midst of a rally and already up about 200 points when the quake was felt, immediately began dropping. The Dow lost 60 points in the next half-hour, though the rally continued once people regained their nerve and the day ended with the index up 322 points at 11,177.

Lou Pastina, head of operations at the New York Stock Exchange, told the AP: “It could have been opportunistic selling.”

• David Hill contributed to this article.