Regional dialects persist on Twitter:

In northern California, something that's cool is "koo" in tweets, while in southern California, it's "coo." In many cities, something is "sumthin," but tweets in New York City favor "suttin." While many of us might complain in tweets of being "very" tired, people in northern California tend to be "hella" tired, New Yorkers "deadass" tired and Angelenos are simply tired "af."

Here's the full academic paper. (Via Marginal Revolution.)