The result moves Crewe above Brighton in the drop zone and, to compound the home team's misery, their squad is ravaged by injury and suspensions.
Their problems began before a ball had been kicked. Nicky Forster, their skipper and top scorer, pulled out during the warm-up with a calf injury.
Brighton then played for the last half-hour with only ten men. They had already used their substitutes when Jim McNulty was forced off with a rib injury.
Crewe were a goal up at that stage, courtesy of a penalty needlessly conceded by Craig Davies.
The striker handled when back helping his defence to clear a free-kick and Billy Jones made no mistake from the spot.
Brighton had already lost centre-half Tommy Elphick to an early injury and his replacement, Adam Hinshelwood, also picked up an injury and did not reappear for the second half.
Brighton almost equalised twice in quick succession straight after the break. On-loan Everton goalkeeper John Ruddy saved Davies' stab goalwards and his follow-up rolled just wide via a deflection.
Adam El-Abd's resulting header from Dean Cox's corner was cleared off the line by Crewe captain Julien Baudet.
Crewe then made their numerical advantage count handsomely once McNulty left the action.
Midfielder Steven Schumacher drove in spectacularly from 25 yards with 11 minutes left.
Jones added his second six minutes from time with a curling free-kick from outside the box.
Substitute Gylfi Sigurdsson, making his debut on loan from Reading, completed the rout with another accomplished finish in the 89th minute.
Brighton already have Adam Virgo suspended for four more games and Cox faces a ban as well after collecting his fifth booking of the season.