For 17-year-old Amanda Sanchez, social networking is an obsession, a distraction — and when she moved to a new town last summer, it was her lifeline.

“Over the summer, MySpace was my best friend,” says the high school junior, who lives in San Dimas, Calif. “I didn’t know anybody after I moved, so I was on there all the time.”

She usually checks her page a couple times a day — and keeps in touch with old friends and those she’s made at her new high school. So preferred is this form of communication among people her age that guys ask her for her MySpace address more often than her phone number.

It’s pretty typical behavior, according to a new survey from the Pew Internet & American Life Project. The survey of 12- to 17-year-olds provides some of the first independent numbers on social networking for that age group — and found that older girls, in particular, are the most likely to have used social networking sites, such as MySpace or Facebook.

The popular sites are among those that allow users to create profiles, swap messages and share photos and video clips, with the goal of expanding their circle of online friends.

The Pew survey, released Sunday, found that 70 percent of teen girls, ages 15 to 17, had profiles on social networking sites, compared with 57 percent of boys in that age bracket.

The numbers remained much the same across racial and economic lines.

“Most teens realize how much of social life is happening in these networks — and that’s something they often want to be a part of,” says Amanda Lenhart, a senior research specialist at Pew.

The survey also found that MySpace was, by far, the most popular site. Of the youth who’d used social networking, 85 percent said they used MySpace, while 7 percent had done the same on Facebook and 1 percent on Xanga.

The survey of 935 U.S. youth, ages 12 to 17, was done by telephone in October and November. The results have a margin of sampling error of plus or minus 3.7 percentage points.

When looking at the entire age bracket — 12 to 17 — Lenhart and her colleagues found that 55 percent said they used social networking sites. Not surprisingly, she said, younger children in that age range were the least likely to do so, with just over a third of 12- and 13-year-olds saying they’d created a profile. Experts say this is partly due to the fact that sites such as MySpace require users to be 14 (though they can lie about their age to gain access).

Danah Boyd, a researcher at the University of Southern California, says the survey results largely match what she’s found in the field when interviewing teens.

That includes findings that girls are most likely to use social networking as a way to maintain contact with current friends, as well as those they rarely see.

“Our brains are attuned to social data. We love gossip. We love details about one another,” Boyd says. “In the process, we build friendships.”

Meanwhile, the survey found that older boys who use social networking were more than twice as likely as older girls to say they use the sites to flirt — 29 percent of older boys, compared with 13 percent of older girls.

“One of the things to take away from this report should be a sense of ‘the kids are alright,’ says Steve Jones, a communications professor at the University of Illinois at Chicago who studies new media. “It’s clear that teens are not just willy-nilly using social networking sites and making themselves vulnerable to predators.

“That is not to say, of course, that there are not some who are careless or even some who seem to invite trouble,” he adds, but says many young people appear to be aware of security.

In the survey, for instance, two-thirds of teens who’ve created profiles said only allowed friends they approved to access their profiles. And most teens knew the difference between a public and private profile.

About half said they used social networking to make new friends — but Boyd says she’s found that, in many instances, that means they’re getting to know “friends of friends,” not strangers.

Still, not everyone is convinced that the social networking trend is a good one.

“Each year, incoming students are more distracted than ever,” says Michael Bugeja, director of Iowa State University’s journalism school and author of the book “Interpersonal Divide: The Search for Community in a Technological Age.”

“These data from the Pew survey verify what we already know — that the situation will get worse before it improves.”