Interesting information. From the above guys that actually know the strength and characteristics of an EMP, their explanations sound pretty solid. I don't know the strength admittedly, but I do deal with "normal" transients on a daily basis. A very short duration pulse, equates to a high frequency even if there is only one pulse. Rate of change will effect the damage and high frequency is a high rate change. I don't know what is capable from a nuclear device, however, so I'll listen to what the others say. Reading the links provided when I have time
I never really put much thought into the EMP phenomenon, because honestly it's not on my radar. A highly unlikely scenario to start with, and if it did happen I'd have bigger fish to fry. I do not include electricity as needed for basic human survival.