It was the second consecutive shutout at home for the Union, both registered by goalkeeper Brad Knighton. Philadelphia beat Chicago 1-0 on Sept. 11.
Sebastien Le Toux scored his team-leading 12th goal in the 69th minute on a free kick for a 3-0 lead.
The Union (7-12-6) had 10 days off before this match, having lost at San Jose on Sept. 15.
Chivas fell to 7-14-4 and 2-9-2 on the road.
In the 26th minute, Justin Mapp lofted a perfect corner kick and Moreno converted with a header past backup goalkeeper Zach Thornton.
Chivas starting goalie Dan Kennedy is out for the season with a torn biceps tendon.
Just as the second minute of stoppage time was about to elapse in the opening half, Fred corralled a loose ball in front of the net and scored for a 2-0 lead.
(Copyright 2010 Philadelphia Union. Reprinted by permission)