I'm just looking at an IMC 7.2 system, and this includes this trap definition by default.
Rather than browsing the MIB tree, you should be looking at Alarm -> Trap Management -> Trap Definition.
Be careful with filtering this trap. It looks like a generic trap, with the parameters used for the specific message. If you block the trap (with no further filtering), you may find you match other events you do want.
The other way of doing this is to find the trap at Trap Management -> Browse Traps. Find the one you want, click on the Description, then click "Filter the Trap." This is probably the easiest way to find the right trap.