Quaking (Weapon Master's Handbook pg. 30)
This special ability can be placed only on melee bludgeoning weapons. The wielder of a quaking weapon can strike the ground as a standard action to perform a trip combat maneuver that applies to all foes within a 5-foot-radius spread, a 10-foot cone, or a 20-foot line along the ground. The wielder can trip creatures of any size this way. This trip maneuver attempt provokes attacks of opportunity unless the wielder has some feat or ability that prevents it, and the wielder can never be knocked prone as a result of failing this special trip combat maneuver check.
Le't say that Bob the Brawler has a magic Mace, with the Quaking Enhancement. He also has, Dexterity 20, Combat Reflexes (for a total of 6 AoO per round), Greater Trip and Vicious Stomp (with all their pre-requisites).
Now, let's assume Bob the Brawler is surrounded by 8 enemies!
The question: Does quaking trigger Greater Trip? Allowing Bob and his allies to make AoO against those enemies, or only Bob's Vicious Stomp would be triggered?