Brandon Belt, Evan Longoria and Brandon Crawford hit home runs and seven San Francisco pitchers combined for 17 strikeouts as the Giants defeated Seattle 9-3 Wednesday night in what was considered a home game for the Mariners at Oracle Park.The two-game interleague series was originally scheduled to begin Tuesday night in Seattle, but hazardous air conditions from wildfires in the Pacific Northwest forced a day off and a move to the Bay Area.Right-hander Trevor Cahill (1-1) pitched two scoreless innings of relief as the Giants (24-24) snapped a three-game losing streak and remained in position for one of the two National League wild-card spots in the expanded postseason.San Francisco built an 8-0 lead through 3 1/2 innings.Mariners right-hander Ljay Newsome (0-1), making his third major league start, allowed five runs on eight hits in three innings, with one walk and one strikeout.Belt hit a two-run shot to right-center field off Newsome to give the Giants a 4-0 lead in the third. An out later, Longoria lined a solo shot over the left-field fence.Erik Swanson, making his first appearance since a stint on the 10-day injured list with a right forearm strain, took over for Newsome in the fourth but lasted just one-third of an inning, giving up three runs (two earned) on four hits and a walk.The Mariners (22-27) scored all of their runs in the bottom of the fourth.Giants left-hander Drew Smyly, making his first start of the season after recently coming back from a finger injury, allowed three runs on four hits in 3 2/ 3 innings. He walked one and matched his season-high with eight strikeouts.Smyly allowed a run-scoring double by Luis Torrens in the fourth before being replaced with two runners on. Lefty Caleb Barager came on and walked all three batters he faced, including the last two with the bases loaded.Crawford hit a solo shot to center field off right-hander Brandon Brennan in the seventh.Seattle’s Dylan Moore was hit in the head by a 99-mph fastball from Giants reliever Sam Coonrod leading off the seventh inning. After being down in the batter’s box for a couple of seconds, Moore took first base but was replaced after the inning.