The San Francisco 49ers completely dominated the Seattle Seahawks in the first half, and never really let the game get close beyond that.

San Francisco marched into Seattle and picked up a 31-13 win in a key NFC West divisional battle on Thursday night.

Seattle's offense looked lost for most of the game and its defense couldn't do much to stop the 49ers outside of one big play in the third quarter.

49ers QB Brock Purdy threw a pick-6 to Seattle's Jordyn Brooks early in the second half to cut San Francisco's lead to 24-10 at the time. Seattle tacked on a field goal to get it to 24-13, but never got any closer.

Purdy closed the door with his best throw of the day, a 28-yard strike to Brandon Aiyuk for a fourth-quarter TD.

That was Purdy's only TD pass of the night as he finished 21-of-30 for 209 passing yards and the one interception.

Christian McCaffrey was the main engine of the 49ers' offense on Thursday, rushing for 114 yards and two touchdowns in 19 carries. He's now at 11 rushing TDs on the season, which is a franchise record.

Deebo Samuel also scored a rushing touchdown in the first quarter.

The Seahawks struggled to get much going on offense all night, scoring only six offensive points while QB Geno Smith took six sacks and didn't get much going in the pass game.

He completed 18 of 27 passes for 180 yards and an interception.

For San Francisco, the win extends its division lead to two games over the Seahawks. Up next for the 8-3 49ers in a massive matchup against the NFC-leading Philadelphia Eagles on Dec. 3.