This improv game is in the following improv game categories:
Audience suggests a type of disaster (flood, earthquake, alien invasion, you name it) and a location where the play will unfold, preferably a location where lots of characters can be found. Examples are a tropical tourist paradise, a big building.
The story starts right before the disaster, usually some character foreseeing the disaster, discovering a bad omen or some foretelling sign.
Next we see lots of characters in the given location. These should be the archetypical characters one finds in typical disaster movies. Examples are:
Next, disaster strikes. Light, sound and smoke effects are a must. Why not use a musician with electric distortion guitar for added color.
The following scenes show the characters in their quest to survive. Most will die (spectacularly). Feel free to provide background on the characters using flashbacks.
Story ends with the hero + lover + kid (if available and/or still alive) escaping the carnage, ready and set to live happily ever after.