The Rams (10-4) avenged an earlier 16-10 loss to Seattle and opened a two-game lead over the Seahawks (8-6) with two games remaining.
Gurley followed a pair of 1-yard touchdown runs with a 57-yarder with 28 seconds left in the first half that put the Rams up 34-0. Gurley added a 14-yard touchdown reception in the third quarter that made it 40-0.
Gurley carried 21 times for 152 yards, and Jared Goff completed 14 of 21 passes for 121 yards with two touchdowns and one interception. Los Angeles outgained Seattle 352-149 in offensive yards and held the Seahawks to just 78 yards on the ground.
Russell Wilson completed 14 of 30 passes for 142 yards and one touchdown, and he led the Seahawks in with 39 rushing yards.
The Rams scored on six of their seven possessions in the decisive first half and did not have to punt. The only time they failed to score was when Goff was intercepted on a fourth-and-1 pass from the Seattle 24-yard line early in the second quarter.
Seattle was held to just 59 yards and four first downs in the first half when Wilson was sacked four times for 47 yards. The Rams began five first-half drives in Seattle territory, including one at the 1-yard line, and another drive at the 50.
The Seahawks finally scored on Wilson's 26-yard pass to Luke Willson with 1:23 left in the third quarter. The Rams added a safety in the fourth quarter when Wilson was called for intentional grounding in the end zone.
Los Angeles took advantage of a turnover, a long punt return and Seattle's offensive ineffectiveness to build a 13-0 lead after three possessions.
The Rams capitalized on a Seahawks fumble for a quick 3-0 lead. On Seattle's third offensive play, linebacker Alec Ogletree recovered Tanner McEvoy's fumble after a 19-yard pass completion at the Seahawks 40-yard line.
Los Angeles moved to the Seattle 18 before settling for Greg Zuerlein's 36-yard field goal.
Seattle was forced to punt following a third-down sack on its next possession and the Rams responded with a seven-play, 37-yard drive, extending the lead to 6-0 on Zuerlein's 31-yard field goal.
The Seahawks started their next possession from their 20 with a holding penalty, then had an apparent 23-yard pass to tight end Jimmy Graham ruled incomplete after review, followed by another sack of Wilson.
Pharoh Cooper then returned the punt 53 yards before being tripped up from behind at the 1-yard line by Neiko Thorpe. Gurley crashed over on the next play to make it 13-0 with 5:57 left in the first quarter.
Cooper set up the Rams' next touchdown with a 26-yard punt return to the Seattle 36. Gurley capped the five-play drive with another 1-yard touchdown run to push the lead to 20-0 with 8:13 left in the half.
On the ensuing possession, Wilson coughed up the ball on a 13-yard sack and defensive end Morgan Fox recovered at the Seattle 39. The Rams needed just seven plays to make it 27-0 with Goff hitting wide receiver Robert Woods on a 1-yard touchdown pass.
Cooper returned Seattle's final punt of the half 26 yards to set up Gurley's 57-yard touchdown run.
NOTES: Among Seattle's inactives was LB K.J. Wright, the team's second-leading tackler, who sustained a concussion last week against Jacksonville. He had started 61 consecutive games. ... Seattle made two roster moves on Saturday, finally putting injured S Kam Chancellor (neck) on injured reserve and waiving G Mark Glowinski, who started the first two games this season. LB Kache Palacio and CB Mike Tyson were added to the roster off the practice squad. ... The Rams avoided their first season sweep against the Seahawks since 2013. ... The 34-0 halftime deficit was Seattle's largest at home since Nov. 7, 2010, when the New York Giants built a 35-0 halftime lead en route to a 41-7 victory. ... Rams PR Pharoh Cooper had four punt returns for 109 yards in the first half, seven for 128 yards in the game. ... Seattle rookie SS Delano Hill was penalized for unnecessary roughness on a punt return scuffle and ejected early in the third quarter.