Think social media has killed search as a traffic driver? Think again, given that social media giant Twitter shared today that SEO has helped it generate a 10-times increase in logged-out visitors to its web site.

The news came during the Twitter Analyst Day event today. Twitter’s director of product management Trevor O’Brien said the company made a change earlier this year to ensure that search engines like Google and Bing could better access 50,000 popular hashtag pages — pages where Twitter has compiled tweets and information relating to a particular hashtag.

For example, if you were interested in the #AlexFromTarget hashtag that went viral last week, you might search for that on Google. If so, Twitter’s hashtag about it ranks in the top results:

People clicking from there land on a page all about the hashtag:

Twitter says making this change increased the number of logged-out users coming to its site by 10-fold, apparently raising the number from 7.5 million per month to the current 75 million per month.

For logged-out users, the main call-to-action on these pages is to encourage them to sign-up for Twitter. However, Twitter is exploring other ideas on how to make money off these pages.

Ironically, Twitter once had huge amounts of Google traffic coming its way through a deal it has struck with the search giant. That deal fell apart in 2011. For more background on that, in light of today’s news, see our companion story on Marketing Land: