7:35pm: The Seahawks have officially announced the transaction, tweets Bob Condotta of the Seattle Times.
The Jaguars released the 30-year-old late last month. Blackmon spent the last two seasons with the Jaguars and been one of the top three cornerbacks for the team during his time there, starting 12 of 23 games. His 2014 campaign was cut short by a broken finger, which landed him on the injured reserve list with about two months left in the season.
Jacksonville wanted to go younger, but Seattle is happy to add the seasoned cornerback to its already loaded secondary. In 2013, Blackmon graded out as the 22nd best cornerback in the league according to the advanced metrics at Pro Football Focus (subscription required).