Surging Seahawks crush 49ers to clinch playoff berth Mon Dec 24, 2012 12:15am EST (Reuters) - The Seattle Seahawks ensured the NFC West title race will go down to the final week with a playoff-clinching 42-13 home rout of the San Francisco 49ers on Sunday. With the division rivals facing off in a rainy Seattle, the Seahawks dominated the first-place 49ers from the start as they remained unbeaten at home and closed to within half a game of San Francisco. The 49ers entered the game with a chance to clinch the division but found themselves on the wrong end of a sound beating by a surging Seahawks (10-5), who have won four straight including the last three by a combined 120 points. San Francisco (10-4-1) can still claim the crown with a home win over Arizona while Seattle needs to beat St Louis and hope for a 49ers loss to leapfrog their rivals. Marshawn Lynch triggered the rout with two touchdowns in the first quarter before Richard Sherman returned a blocked field goal attempt 90 yards to give Seattle a 21-0 lead at the start of the second as the home crowd were whipped into a deafening frenzy. Rookie quarterback Russell Wilson added touchdown passes in each of the final three quarters, finishing the game with four, to emphatically outplay San Francisco's second-year signal caller Colin Kaepernick. The young Kaepernick often appeared flustered and disorganized by the raucous crowd noise as the 49ers were rendered helpless by the stout Seahawks defense. Adding injury to the insult of a heavy defeat, tight end Vernon Davis (concussion) and receiver Mario Manningham (knee) were both knocked out of the game. Lynch finished with 111 yards rushing and Seattle punished San Francisco with the type of bruising style usually attributed to the 49ers. Writing by Jahmal Corner; Editing by John O'Brien