The subject of the document is entitled “National Continuity Policy.”
It defines a “catastrophic emergency” as “any incident, regardless of location, that results in extraordinary levels of mass casualties, damage, or disruption severely affecting the U.S. population, infrastructure, environment, economy, or government function.”
This could mean another 9/11, or another Katrina, or a major earthquake in California, I imagine, since it says it would include “localized acts of nature, accidents, and technological or attack-related emergencies.”