The Pittsburgh Steelers erupted for 20 points before Miami could even make a splash and then used a stifling defense to slug the Dolphins, 34-14, in the AFC semifinal championship game today.

The victory sends the three-time Super Bowl champs into next Sunday's AFC title game here against Houston in a replay of last year's clash between the two Central Division rivals.

The Steelers were so dominant today that the Dolphins managed only 25 net rushing yards for the game. Miami failed to get a first down in the first period.

Twice in the second quarter, Miami got inside the Pittsburgh 10-yard line, but failed to score.

Quarterback Terry Bradshaw demonstrated on the Steelers' first touchdown thrust that they could do what Coach Chuck Noli said they had to do -- run on Miami -- in a 62-yard flouting of the reputed Dolphin strength against the rush.

Franco Harris and Sidney thornton, constituting the Steeler "big-back offense," accounted for 29 of those yards, with Thornton punching over.

Pittsburgh came back with another 62-yard assault in the same period, and this time, Harris 225 pounds, and Thornton, 230, accounted for 36 yards before Bradshaw passed 17 yards to wide receiver John Stallworth for the touchdown. Matt Bahr's conversion attempt was blocked.

Then Bradshaw put the Dophins out of it with a 56-yard attack, needing little help from his ground game as he passed 16 yards to Thornton and 20 to wide receiver Lynn Swann for a touchdown and a 20-0 first-period lead.

The fast start appeared to be fortunate for the Steelers, because Swann suffered a hamstring aggravation in the second quarter that may cause him to miss the championship game, and Thornton missed most of the second half with an ankle sprain.

But the injuries served to display Pittsburgh's depth. Jim Smith replaced Swann and caught four passes for 41 yards. Rocky Bleier replaced Thornton and scored a touchdown. Harris ended up with 83 yards on 21 carries, including a five-yard scoring run, and caught five passes for 32 yards.

Thornton ran for 52 yards on 12 carries and caught three passes for 34 yards. He was playing for the first time in seven games after recovering from an ankle injury.

Bradshaw was accurate on 21 of 31 passes for 230 yards, with no interceptions. At one point, he had produced on seven third-down challenges, three of them for touchdowns. He finished with seven successful third-down conversions in 10 tries.

It was 24 degrees at kickoff, the first time this season that the Dolphins had played in temperatures below 60. Dolphin quarterback Bob Griese left the pregame warmup with his hands in pockets sewed onto his jersey.

Griese was sacked twice and intercepted once in the first half as the Dolphins netted only seven yards rushing and 28 yards passing.

Griese, 34, had been bothered by a muscle pull in his right leg that made it difficult for him to follow through on long passes, but he did complete one for 40 yards to wide receiver Nat Moore in the third quarter, to the Pittsburgh 20-yard line, but it was unavailing. The Dolphins moved 63 yards to the Pittsburgh six-yard line in the second quarter, but on second-and-six there, a safety blitz by J. T. Thomas of the Steelers made Griese hurry his throw and the ball was intercepted by linebacker Dennis Winston.

The Dolphins appeared to take Griese off the hook when, two plays later, Thornton fumbled the ball away to linebacker Larry Gordon at the Steeler five-yard line.

But on fourth-and-two at the pittsubrg two, Griese threw behind tight end Bruce Hardy, who was unable to make his turn properly because of teammate Moore being knocked into him.

Griese produced a touchdown after 33 minutes 55 seconds, but the seven-yard scoring pass to Duriel Harris in the third quarter was tainted, coming after official Dean Look ruled that Dolphin George Roberts' punt hit Dwayne Woodruff of the Steelers on the back of the leg before being recovered on the Pittsburgh 11-yard line by Don Bessillieu. Griese connected with Harris on second and six.

Dolphin Coach Don Shula replaced Griese with Don Strock with 8:55 to go in the game. Strock took the Dolphins 76 yards to a score, on a one-yard plunge by Larry Csonka, the 33-year-old fullback who might have been playing the last game of his career. He gained 20 yards on 10 carries.

Griese, who was sacked three times, wound up with 14 completions on 26 attempts for 118 yards. Strock was eight of 14 for 125 yards and one interception.

Shula said after the game, "I had bigger and better plans for this team. If anything comes out of this, it is how far we have to go."

Noll, a onetime assistant to Shula, had to field a loaded question: What did he learn from Shula?

"Everything I know . . . and from (assistants) Bill Arnsparger and John Sandusky," Noll replied.