Every electronic device can be affected by an EMP if it's not designed in a way to be shielded against it. The question is, which electronic safe locks are built to withstand an EMP?
We can't speak to every lock out there, only what we know. Of the brands we sell, Sargent & Greanleaf and SecuRam electronic locks have been successfully tested at a MIL-STD 461F rating. This is the level of security created for and used by the Department of Defense for everything they don't want affected by an EMP. It's a high standard. So yes, you can trust Sargent & Greenleaf and SecuRam locks to protect your safe against EMP attacks.
So, what if you want to find out if your electronic lock is EMP tested and approved? If there's not a sticker on the door of the safe, your best bet is looking up the lock manufacturer to see if they bring it up themselves. It's they've passed the test, they'll proudly let you know somewhere on their website. If there's no mention of it, it's very likely they don't have it. Most locks have their name (or their initials) right on the lock itself, if you need to know who made it.