Sainey Nyassi put the Revs ahead with a deflected shot from the edge of the area in just the third minute before Tyson Wahl hit back for the Sounders in the 34th with a brilliant free-kick from outside the box.
Alvaro Fernandez made it 2-1 just six minutes later when he finished from a tight angle after Mauro Rosales’ through ball was knocked on by Roger Levesque to give the home side the win.
In Dallas, the home side produced a 4-0 victory over Portland Timbers thanks to goals from Zach Loyd, George John, Brek Shea and Jackson Goncalves to put last season’s runners-up equal on points with Seattle and now just four in arrears of the Galaxy who were held to a scoreless draw by San Jose Earthquakes.
In the East, Philadelphia Union moved to the top with a hard fought 3-2 win over Chivas USA thanks to an 82nd minute winner from Danny Mwanga as the Red Bulls relinquished a lead to draw 1-1 with Chicago Fire to drop to second.
Elsewhere in MLS, Houston Dynamo scored a late leveler through Brian Ching to draw 2-2 at DC United, Sporting Kansas City beat Vancouver Whitecaps 2-1, Alvaro Saborio scored twice as Real Salt Lake defeated Toronto FC 3-1 as Columbus Crew had a big 4-1 win over ten-man Colorado Rapids.
2011 MLS season – Week 15 scores
San Jose Earthquakes: 0
LA Galaxy: 0 (red card: Josh Saunders 43’)
Buck Shaw Stadium, Santa Clara, CA – 10,872
Sporting Kansas City: 2 (Omar Bravo (p) 33’, Julio Cesar 40’)
Vancouver Whitecaps: 1 (Camilo Sanvezzo 15’)
LIVESTRONG Sporting Park, Kansas City, KS – 18,467