SAN FRANCISCO -- After the San Francisco Giants exploded for 19 hits Tuesday night, their highest total at home all season, first baseman Brandon Belt was asked if the offensive momentum might carry over to the Wednesday game.

His response: Why stop there?

"You've heard a lot that hitting is contagious. I really believe that," Belt said after he contributed a single, a double and a triple to the Giants' 12-3 thumping of the Colorado Rockies.

"Tomorrow, a whole series ... heck, even the rest of the season," Belt continued. "We've got that confidence back. See the ball and square it up."

Buster Posey and Hunter Pence hit back-to-back home runs, and Brandon Crawford had two triples among four hits as the Giants opened a critical six-game homestand with a bang.

"Pretty much our goal all the time is: take the pressure off the pitcher as much as possible," Belt said. "Fortunately, we did that tonight."

The beneficiary was left-hander Matt Moore. He struck out a career-high-tying 11 and allowed only one run in 7 2/3 innings, helping the Giants (83-74) remain a game ahead of the St. Louis Cardinals (82-75) in the battle for the second National League wild card.

The New York Mets (84-74) also won Tuesday and maintained a half-game lead on San Francisco for the first wild card.

"Great all-around game," said Giants manager Bruce Bochy, whose team was coming off a 3-4 trip. "It's good for the guys to bust out. Hopefully that's something that gets them going."

The homers by Posey, his 14th, and Pence, his 13th, came during a four-run fifth inning that broke the game open and ended the night for Rockies rookie right-hander German Marquez (1-1).

With the Giants leading 2-1, Denard Span got the big inning going with a double. He scored on Belt's third hit of the game, a single.

After Belt was thrown out trying to stretch his single into a double, Posey lined a shot into the bleachers in left field to increase the lead to 4-1.

The hit was the 1,000th of Posey's career, all as a Giant. The last Giant to accomplish that feat had been Rich Aurilia in 2003.

Posey's homer was just the second in his past 59 games.

Three pitches later, Pence followed with another solo shot, making it a 5-1 game.

The back-to-back homers were the Giants' fifth of the season.

"Home runs are nice," Bochy said. "We don't hit a lot of them, but they sure help the cause."

The barrage against Marquez wasn't done. Crawford smacked his first triple and scored on a single by Angel Pagan to make it a four-run inning.

That was it for Marquez, who allowed six runs and 12 hits in 4 1/3 innings. He struck out two and did not walk a batter.

"These are opportunities for growth for pitchers like Marquez," Rockies manager Walt Weiss said of his 21-year-old, who was coming off five-inning, one-run effort in an 11-1 home win over the Cardinals. "(He's) obviously very talented, but there's always things to learn at the major league level, and he's doing that now."

Moore (5-5 with the Giants, 12-12 overall) won for the third time in his past four starts. He allowed six hits and no walks in 7 2/3 innings.

"We couldn't afford any more bad starts," said Moore, whose 11 strikeouts matched his total from Sept. 11 against the Arizona Diamondbacks and two times previously in his career while with the Tampa Bay Rays. "We needed to change direction and get it going right now."

Belt had two shots at a cycle after completing three-quarters of the feat in his first three at-bats, but he grounded into a double play in the sixth inning and grounded out in the eighth to finish 3-for-5.

Crawford's second triple came in a five-run eighth inning off the Rockies' fourth pitcher, Justin Miller. The two-run blow scored Posey and Pence.

The hits were Crawford's first since the shortstop dislocated his left pinkie finger on Sept. 20 against the Los Angeles Dodgers.

Conor Gillaspie capped the inning with a two-run homer, his sixth of the season.

Pence finished with three hits, while Span, Pagan, Gillaspie and Joe Panik added two hits apiece for the Giants, who entered the game having scored the fewest runs in September (84) of any major league team.

Ten of the Giants' hits went for extra bases.

"I felt very comfortable," said Marquez, who gave up six of the Giants' 10 extra-base hits. "Give credit to them. I battled."

Nick Hundley had a pair of singles, while David Dahl, Cristhian Adames and Stephen Cardullo all doubled for the Rockies, who had split the first 16 games against the Giants this season.

Cardullo's double drove in a run in a two-run ninth inning for the Rockies against the Giants' third pitcher, Josh Osich.

Colorado, which has lost eight road games in a row, finished with eight hits.

NOTES: The Giants' previous high for hits in a home game this season had been 18, which they reached twice. ... The Giants had four triples in the game, matching a San Francisco-era record for a home game. ... With 3B Eduardo Nunez (strained hamstring) a question mark this week, the Giants acquired INF Gordon Beckham from the Atlanta Braves in exchange for minor league SS Rich Rodriguez. Beckham was in uniform for Tuesday's game. ... The Giants also promoted C Tony Sanchez off the roster of Triple-A Sacramento. ... To make room for Beckham and Sanchez on the 40-man roster, the Giants designated LHP Matt Reynolds for assignment and placed OF Mac Williamson (strained quad) on the 60-day disabled list. ... Giants RHP Johnny Cueto (strained groin) threw a bullpen session before the game and was deemed healthy enough to start the series finale Thursday against the Rockies. Cueto would be a possibility for the National League wild-card game next Wednesday should the Giants get in.