SAN FRANCISCO -- San Francisco Giants first baseman Brandon Belt insists it's harder to hit a triple than a home run.

Surely, his career numbers -- 54 homers, 12 triples -- support that belief.

But after a career first Thursday afternoon, the gap has narrowed.

Belt lashed two of the Giants' four triples, highlighting a 19-hit attack that produced a 13-8 victory over the San Diego Padres.

In recording the most triples the Giants ever had in a game at AT&T Park, San Francisco posted a second consecutive win and a 2-1 series advantage over their National League West rivals.

"We haven't had a game like this in a while," said Giants manager Bruce Bochy. "It's good to get the bats going a little bit. We're missing (left fielder Nori) Aoki and (right fielder Hunter) Pence. We're going to have to get the other guys going."

The Giants recorded season-highs in runs and hits. The four triples were half the team total of eight extra-base hits, another 2015 best.

Right-hander Chris Heston was the beneficiary. He pitched seven innings for his eighth win, tops among NL rookies, helping the Giants finish their first set of back-to-back victories at home since May 28-29 and cap their first series win at home since May 19-21 against the Los Angeles Dodgers.

Belt, who had just one triple in the Giants' first 73 games, connected on consecutive at-bats for near-identical liners into AT&T Park's so-called "triples alley" in right-center field.

The first scored second baseman Joe Panik and capped a two-run first inning against Padres starter James Shields. The second came with one out in the fourth and triggered a three-run uprising that increased the San Francisco lead to 5-0.

"When I sniff a triple, I'm going to turn it on," said Belt, who couldn't recall a game at any level in which he recorded a pair of triples. "Do whatever I need to do to get to third base."

The two 270-foot sprints had Belt thinking big afterward.

"I'm going for (center fielder Angel) Pagan's record," he said of the Giants' West Coast-era record of 15 triples, set by Pagan in 2012. "It took me a while to get started. Now that I know what it feels like, I'm going for it."

Third baseman Matt Duffy led off a two-run fifth with a triple and shortstop Brandon Crawford contributed an RBI triple to a two-run seventh inning as the Giants built 7-0 and 9-2 leads before holding on.

Right fielder Matt Kemp belted a two-run homer, his fifth home run of the season, and shortstop Alexi Amarista added two run-scoring singles, helping the Padres use a two-run seventh and a six-run eighth to get within 9-8.

San Diego got the potential tying run to third base with two outs in the eighth, but pinch-hitter Clint Barmes, batting for the second time in the inning, fouled out to Belt with Padres on first and third.

"There are no moral victories," Padres manager Pat Murphy said. "We haven't played well. Now it's time to get back home and regroup."

The Giants tacked on four insurance runs in the last of the eighth on an RBI single by Duffy, a two-run double by catcher Buster Posey and an RBI double by Crawford.

"The good thing today," Bochy said. "When they scored, we answered back. After that (eighth inning), it's a one-run game. Anything can happen. We had to fight there."

The Giants previously had countered a two-run Padres seventh with two of their own in the bottom of the inning, creating the 9-2 cushion.

Posey's eighth-inning double was his second of the game and third hit overall. He scored three runs and drove in three.

Belt and Panik also had three hits for the Giants. Crawford finished with a double, triple and two RBIs, and right fielder Gregor Blanco drove in three runs with two singles and a sacrifice fly.

In winning his second consecutive start, Heston (8-5) allowed two runs and five hits in seven innings. He walked one and struck out six.

Heston also contributed to the Giants' offensive explosion with a run-scoring single in the fourth.

Kemp, Amarista and reserve infielder Yangervis Solarte had two hits apiece for the Padres, who finished an eight-game trip with a 3-5 record. San Diego has yet to win a road series against an NL West team in seven tries this season.

Both of Solarte's hits came in a pinch-hitting capacity in the six-run eighth. He led off the inning with a double and later got the Padres within one with an RBI single.

Shields (7-2) took the loss, allowing nine hits and a season-worst seven runs in four innings. He walked two and struck out seven.

"I felt like I was pitching well," Shields said. "They got a bunch of hits where I executed my pitch and they just found some holes. I was making my pitches. Unfortunately, it didn't work out for me."

NOTES: The last Giant to record two triples in a game was 1B/OF Brett Pill on Sept. 17, 2011, at Colorado. ... Giants RF Gregor Blanco's multiple-RBI game was his first of the season. ... Three Padres -- INF Yangervis Solarte, SS Clint Barmes and INF Brett Wallace -- recorded pinch hits in the loss. The club hadn't accomplished that feat since May 10, 2005, at Cincinnati. ... Padres RHP James Shields batted eighth, the first time in his career he has hit anywhere other than ninth. He struck out in his only at-bat. ... Giants manager Bruce Bochy disclosed he met with members of his starting staff before the game and gave a heads-up on pending changes when injured RHP Matt Cain (strained flexor tendon in right arm) and RHP Jake Peavy (strained back) make expected returns in early July. The current plan is to demote RHP Tim Lincecum to the bullpen and place RHP Tim Hudson on the disabled list. ... Baseball commissioner Rob Manfred attended the game and told reporters that a second replay center is in the plans. It would be located in San Francisco. The current one is in New York.