CHICAGO -- Previous Chicago Cubs teams might have wilted in the same situation.

However, the National League's hottest team keeps finding ways to win, or at least persevere, as was the case Sunday in the Cubs' 2-0 victory over the San Francisco Giants that completed a four-game series sweep.

Right-hander Jake Arrieta (13-6) reached a career high in victories while tossing 7 2/3 innings of four-hit shutout ball. Reliever Justin Grimm recorded the final out in the eighth.

Chicago closer Hector Rondon loaded the bases in a nervous ninth, then struck out three consecutive batters for his 19th save.

"In the past at times we maybe let a game like that slip away, which from time to time over 162 is going to happen," Arrieta said. "But at this point in the season, if you have the opportunity, you've got to close those out."

The sweep was the Cubs' first of the Giants at Wrigley Field since June 9-12, 1977.

About an hour after the game, the ballpark was cleared of all media members and grounds crew and cleanup personnel after reports of a "credible bomb threat," according to security. Cubs security and Chicago police, some with bomb-sniffing dogs, were observed checking the facility.

Chicago (62-48) won for the ninth time in 10 games and moved 3 1/2 games ahead of San Francisco (59-52) in the race for a second National League wild-card playoff berth.

The Cubs also reached a season-best 14 games over .500.

Arrieta departed with two outs in the eighth after giving up an infield single to Giants third baseman Matt Duffy. He struck out six and walked just two.

In the ninth, Rondon gave up a leadoff single to Giants first baseman Brandon Belt, a double to right to shortstop Brandon Crawford and hit second baseman Ehire Adrianza with a pitch.

Rondon then struck out pinch hitter Hector Sanchez and center fielder Angel Pagan and got left fielder Gregor Blanco on a called third strike to end the game.

"We had a golden opportunity and couldn't quite get it done," Giants manager Bruce Bochy said. "It didn't play out like we all thought it would -- bases loaded, nobody out. Give him (Rondon) credit, but I thought he got a little help. That (final pitch) was ball four."

Giants right-hander Jake Peavy (2-5) worked five innings in his seventh start since coming off the disabled list on July 3. He gave up two runs on four hits and two walks with six strikeouts.

He threw 101 pitches, including 69 strikes. The Cubs fouled off 37 pitches.

"If we were in another ballpark, there's 10 foul-ball outs," Peavy said. "Those would have saved a lot of pitches, and I could have went deeper in the game."

The Cubs, who trailed only once the entire series, scored single runs in the first and second innings to give Arrieta the early lead.

Chicago made it four straight games with at least one first-inning run as third baseman Kris Bryant's bloop single to right scored left fielder Kyle Schwarber.

The Cubs made it 2-0 in the second when Arrieta tripled off the right field wall with one out, setting up a sacrifice fly to center by second baseman Addison Russell.

It was the second career triple for Arrieta, a lifetime .144 career batter who had has only other three hits in 2014.

"Jake was outstanding, even his lumbering triple was interesting to watch," Cubs manager Joe Maddon said. "You're really happy that he thought three because he made it rather easily. Most pitchers in that situation would not be going for three bases."

Giants left fielder Nori Aoki left the game in the third inning after being was struck on the helmet by an Arrieta pitch. He walked off unaided, and Pagan came in as a pinch runner and remained in the game.

Later reports from the clubhouse indicated Aoki was fine.

NOTES: The Giants had not lost a series at Wrigley Field since 2008 until the current trip, winning four and tying three until the Cubs swept the four-game series that concluded Sunday. ... San Francisco relievers have had a rough go of late, giving up 18 runs (16 earned) in 31 2/3 innings in nine games on the road trip through Saturday. Giants relievers pitched three shutout innings Sunday, however. ... The Giants are idle Monday before opening a six-game homestead Tuesday as LHP Madison Bumgarner (12-6, 3.28 ERA) goes against Houston Astros LHP Scott Kazmir (6-6, 2.08 ERA) on Tuesday. ... Cubs 3B Kris Bryant played in his 100th career game Saturday, and he has 15 home runs and 65 RBIs. The last Cub to do so in his first 100 games was Vince Barton (16 homers, 65 RBIs in 1931-32). ... The Cubs have Monday off, then continue their homestand Tuesday in the opener of a three-game series with Milwaukee. Cubs RHP Dan Haren (7-7, 3.49 ERA) makes his second start since being acquired, facing Brewers RHP Taylor Jungmann (6-3, 2.26 ERA).