Photos of the storm were popping up on many social networks including Twitter and Google+, but Instagram data showed at least 521,000 photos with the hashtag Sandy.
Another 306,000 were tagged #hurricaneSandy and 39,000 tagged #Frankenstorm.
Jeff Sonderman, a digital media fellow at The Poynter Institute, said that at one point Instagram was posting 10 pictures of the storm per second.
"Natural disasters and tragedies are emerging as a way for social media services to gain respect and legitimacy as world-changing agents as well," he said.
"You can see why a national disaster as told through Instagram could be powerful. In theory, Instagram has Twitter's immediacy, and a broader reach, since it pushes notices out via Twitter, Facebook, Instgram's own network, and email. Clearly images are the best way to tell a story like this, and Instagram's whole raison d'etre is to make people better photographers."
On Twitter, some 147,000 pictures were posted over a 24-hour period tagged Sandy.
Some of the pictures, however, were fakes. A Tumblr page sought to keep track of the obvious and less-obvious bogus photos as "a public service."
One dramatic shot of the New York skyline was "actually a picture from 2011, of a thunderstorm over Manhattan during a tornado alert," said the Tumblr blog author identified as @flashboy.
Facebook completed its acquisition of Instagram in September. The original price was pegged at $1 billion but the final value was less because of the decline in Facebook's share price.