NFL Network insider Jason La Canfora, citing a league source, reported at Hawthorne receives a $350,000 signing bonus and a prorated $220,000 bump in 2010 salary. He will earn $900,000 in 2011 and can claim $100,000 in roster bonuses in 2010 and 2011.
The team confirmed the signing Tuesday.
Hawthorne leads Seattle with 66 tackles and has one interception. He has moved into the starting weakside linebacker spot in Seattle's defense, replacing Leroy Hill, who is on injured reserve.
Hawthorne's first break came last year when he took over the starting spot when middle linebacker Lofa Tatupu was lost for the season with a pectoral injury.
Hawthorne was signed as an undrafted free agent out of TCU before the 2008 season.
The Associated Press contributed to this report.