SEATTLE -- The mistakes began piling up for Houston at the opening coin toss, when the referee inadvertently referred to the Texans as "Dallas."
And that's about the same time the yards started piling up for Seattle.
Seattle set a franchise record with 320 yards rushing: Alexander ran for 141 and his backup, Maurice Morris, added 104. Not that Seattle seemed surprised by their easy win.
"This team is finally getting to where it should be," Alexander said. "We're mature. We handle our business."
The Texans, meanwhile, are now the NFL's only winless team at 0-5.
"It's frustrating ... because at 0-5 it's going to be easy to jump off the bridge," quarterback David Carr said after enduring three more sacks in a 19-of-33 performance for 179 yards and one touchdown.
Carr has struggled all year behind an injured and shuffled offensive line that has allowed a league-leading 30 sacks.
Houston coach Dom Capers looked both angered and befuddled.
"I'm very disappointed in the way we played tonight," Capers said. "The thing I was most disappointed in was basically the fundamentals of our team."
One week after a huge win at division rival St. Louis, the Seahawks breezed through this potential letdown to go to 4-2.
"It's good to have a win, but this is a team we should have beaten," veteran center Robbie Tobeck said. "That's the thing that's encouraging -- not the fact we won this game, but that we didn't slip and make it a close game."
Quarterback Matt Hasselbeck had an efficient 14-of-20 passing night for 168 yards and an easy 3-yard touchdown toss to receiver Joe Jurevicius. Hasselbeck did throw his first interception after a franchise-record streak of 159 passes without one, late in the first half. But by then, Seattle led 21-3.
The Seahawks are now primed to control their relatively weak division; the second-place Rams are 2-3 and have an ominous task Monday night at 5-0 Indianapolis. Seattle's next order of business, meanwhile, is the real Dallas Cowboys, who come west for a showdown of division leaders next Sunday.
Alexander scored on runs of 4, 5 and 1 and 23 yards. The third ended Seattle's initial drive of the second half and extended Seattle's lead to 28-3 in the third quarter. The four rushing TDs equaled his quadruple Sept. 25 against Arizona and was the third such feat of his career.
The NFL's leading runner extended his franchise record to 26 career games with at least 100. He has 718 yards rushing through six games, after finishing one yard shy of the New York Jets' Curtis Martin for the league rushing title at the end of 2004.
The six-year veteran also has 74 career rushing touchdowns. That ties him with Earl Campbell and Leroy Kelly for 18th all-time.
After Alexander's fourth score, which put Seattle ahead 35-10 early in the fourth quarter, the noted post-score showman pantomimed rocking and burping a baby. Earlier, after his first TD 6:48 into the rout, he grabbed the back of his helmet with his right hand and repeatedly pumped his elbows in a rotating motion, like a sprinkler.
"One of the coolest things in the game is scoring touchdowns," Alexander said. "That's what still drives me."
Then came the rain of Houston errors. The Texans' 25th-ranked defense was flagged for hands to the face, pass interference, illegal use of hands and holding -- and that was just in the first half. In all, Houston had 13 penalties.
Meanwhile, Houston's last-ranked offense, averaging just 213 total yards and 11 points per game entering Sunday, actually improved. It had to 227 total yards.
The Texans' best chance to stay in the game came and went midway through the second quarter. With Seattle ahead 14-0, Carr completed five straight passes -- including a fourth-down one to Jabar Gaffney -- during an 18-play drive to the Seahawks 20. But then Carr fumbled a snap and lost five yards on his recovery. That left the Texans with Kris Brown's 39-yard field goal as consolation. They still trailed 14-3, and never got closer.
- The 100-yard rushing nights from Alexander and Morris was the third time in Seattle's 30 seasons a duo has reached that milestone in the same game. Curt Warner and John L. Williams did it twice, Nov. 28, 1988 and Dec. 11, 1988.
- Seattle sacked Carr three times. Carr has been dumped 30 times through six games, still on pace to break his own single-season NFL record of 76 from his rookie season of 2002.
- Texans Pro Bowl receiver Andre Johnson missed the first game of his 36-game career because of strained right calf, which he injured Oct. 9 against Tennessee.