Pick a composition of asteroid. Pick a diameter. Pick a speed. Pick an angle of impact. Pick a location on the planet. Watch how much damage, what kind of damage, and what the blast radii would be.
The CERT concept was developed and implemented by the Los Angeles City Fire Department in 1985. The Whittier Narrows earthquake in 1987 underscored the area-wide threat of a major disaster in California. Further, it confirmed the need for training civilians to meet their immediate needs.
An Open Streetmap effort to build maps of places that are underserved. Humanitarian effort to fill in the blanks where companies don't or won't reach.
An interesting article discussing a hierarchy of potential eschatological events.
An interesting bit of historical text originally published by Oak Ridge National Labs on the topic of surviving a nuclear war.