The two MLS sides also included draft picks in the deal that sees the Sounders continue to offload last year's team.
Ianni and Hurtado have both been regulars on the back line for Seattle since the club came in to Major League Soccer, racking up almost 200 regular season appearances between them.
In return the Sounders get the 25-year-old Anibaba, a defender who also has substantial MLS experience, including starting all 34 regular season matches for the Fire in 2013.
The trade is just the latest move in an offseason that has seen the Sounders completely re-shape its roster after a disappointing end to 2013. Star forward Eddie Johnson and midfield playmaker Mauro Rosales are the two most notable departures to date, with Anibaba joining the likes of Chad Marshall and Kenny Cooper as players headed to Seattle.