The Astros' 22 hits tied for the sixth most in club history. It's the most runs and hits for the Astros since an 18-4 win over St. Louis on Aug. 3, 2010.
"It was only a matter of time," said Bo Porter, who earned his first road win as a manager. "We've had confidence the whole time they can hit. It was unfortunate the games prior to tonight that we had not hit, but it was good to see."
Houston, which scored only nine runs during its six-game skid, had matched that total by the second inning and nearly matched its run total (17) from the first seven games of season.
"We're going to take this day like a wake-up day," said Astros second baseman Jose Altuve, who went 4-for-6 with a homer and set a career high with four RBIs.
The Astros walloped five homers, with Chris Carter hitting two in his first career multi-homer game, and J.D. Martinez, Marwin Gonzalez and Altuve also hitting their first of the season.
"Hopefully this keeps rolling for us and we keep on winning," Carter said.
Porter never flinched during the Astros' early woes, saying he knew his club was due for a breakout performance.
"Like I told you guys the whole time, I was never really concerned," he said. "It's a long baseball season. I've been in this game a long time. I've played, I've coached, and you can never get alarmed in any stretch. As well as we played tonight, tomorrow we have to come back and it's a new ballgame."
Astros starter Erik Bedard, making his first start for Houston and first appearance at Safeco Field since pitching for the Mariners from 2008-11, threw four scoreless innings, allowing one hit. He left with a 13-0 lead but didn't go deep enough to qualify for the win after hitting his pitch limit.
"I don't change anything," said Bedard, who threw 66 pitches. "I throw like it was a 0-0 game and you can't let the score do too much to the way you want to throw. You keep battling, you keep throwing strikes and the rest will take care of itself."
The Astros sent 11 batters to the plate in the first and bashed out six hits and seven runs to chase starter Brandon Maurer (0-2) after two-thirds of an inning. Carlos Pena's bases-loaded double scored a pair to get the offense going. Martinez and Matt Dominguez added RBI singles, and Altuve's two-run double made it 6-0.
"It's a tough game," Seattle manager Eric Wedge said. "I just told him to keep his head up when he was walking off the field. It's the big leagues and sometimes it doesn't matter what you do.
Carter cranked a homer in the second off reliever Kameron Loe, and Martinez hit a two-run homer to left-center moments later to push the lead to 9-0. Loe gave up a third homer, a solo shot by Gonzalez in the third that made it 10-0.
"They did a good job managing their at-bats and keeping the line moving," Porter said. "Even before we got the home runs, it was singles, doubles, line drives. It was what we talk about all the time, keep the line moving and make the pitcher work, and those guys did a tremendous job of that."
Martinez had been removed from the game a night earlier for his approach during an at-bat in the fourth inning, but Porter put him back in the lineup Tuesday and it paid off. The homer was Martinez's first since July 4, 2012, a span of 141 at-bats.
"You could feel that tension and anxiety that was built up, and once you let that go ..." Martinez said. "I felt like right away, in the first inning, we got guys on base and we got some big hits and we got it going right there. Everybody felt that relief, like, 'OK, all the pressure's not on me now. We got a lead and let's just hit.' You felt that in the dugout."
Altuve launched a two-run homer in the fourth to push the lead to 13-0, matching a career high with four hits. Seattle pushed across a couple of runs in the fifth on a pair of sacrifice flies off Paul Clemens, who worked four innings -- allowing three solo homers -- in his Major League debut and got the win -- and a shaving-cream pie in the face.
"It was an adrenaline rush," Clemens said. "It was an unbelievable feeling. It was a dream come true and that was the most important thing. My teammates were all in my corner, and it was an exciting time."