Lets try this one:
Even if said safe were plugged into 120VAC for power I think they use batteries for the computers in the locks. At the vey least the 120VAC would be cut back to low voltage DC just like the computer your looking at right now to operate anything other than the safes dehumidifier & lights. The solenoids that actually pull back the locking bars are going to be operated by 12VDC or less (UL would never allow AC current to be used in a home safe for this). I've yet to see the keypad that couldnt be smashed with a hammer and chisel, or hacksaw. Once inside the keypad you only have to trace the wires going out to the solenoids (very easy to locate), touch a 9 volt battery to the leads, and walla! Open sesame!
If one 9 volt doesnt have enough juice (my bet is it would be enough), use two in series!
Locks only exist to keep honest people honest. A dishonest, or determined person given enough time WILL defeat any lock. If a human mind created it, a human mind can defeat it.
Batteries rely on internal chemical reaction - Not effected by EMP. You just wont be plugging anything in to recharge them once they go dead is the threat to them.