CHICAGO — Scammers emerge as predictably as earthquake aftershocks following natural disasters, making it imperative for consumers to be wary of unsolicited appeals to aid victims in Haiti. The FBI and security experts warned Thursday of the likelihood of scams as requests for donations start pouring in via e-mail, text message, telephone and Twitter. Their key advice: Look carefully before you give money or personal information, and contribute to a known group. Evidence of potential fraud has already surfaced. More than 400 Internet addresses related to Haiti have been registered since the quake, Internet security expert Joel Esler said. The warnings shouldn’t dissuade donors from giving, however. Many organizations are in need; a list can be found at the Foundation Center Web site at foundationcenter.org, among others.