The home side made it four straight wins and seven out of eight thanks to some good fortune in the dying moments.
The Sounders (14-8-4) made it four straight wins and seven out of eight, riding a late own goal to a 2-1 win over the Chicago Fire (10-11-5) on Saturday.
The visitors struck first in the 25th minute. Kept onside by the lagging Djimi Traore, Mike Magee connected with Dilly Duka's through ball, went in alone on Michael Gspurning and slotted his shot home. His 15th of the season, the strike tied him with Marco Di Vaio for the league lead.
Seattle had a golden opportunity to equalize five minutes later when Bakary Soumare was called for a handball in the box. But Sean Johnson guessed right on Osvaldo Alonso's penalty kick, pushing it aside.
The Sounders, however, did draw even in the 40th minute. After Johnson only got a weak punch on a ball in the box, Marc Burch quickly played a pass back to the scrum in front, where Lamar Neagle converted his chance.
In the 89th minute, Seattle got the winner. Striding down the left flank, Zach Scott struck a low centering feed that deflected off Chicago left back Gonzalo Segares and in.