Underground Caves, Earthquakes and Scuba Gear

A few questions:

1. If 1 or 2 million people are living in caves in Missouri, what infrastructure would be in place to support them? Im talking water, food, OXYGEN -- is this all even feasible? Would they be able to grow crops in the caves? What would they use for power and fuel?

2. Did the comet create any sort of quake when it struck the earth? Thinking back to the Tsunami that hit Japan a few years back, seems there was an earthquake and then the wave hit about an hour or 2 later. The massive wave in the movie seemed much quicker, which I can understand. But was there any sort of earthquake? I could see it causing a massive quake that would take out many buildings before the wave even arrived

3. If you were on the coast or within range of it and the tidal wave, instead of running inland (and getting stuck in the flux of people), do you think people could potentially hunker down with scuba gear and just deploy it after the wave washes over them? Naturally they would need to secure theirselves from the rush of water, and even then they could possibly survive that, they would just be pushed for miles in the rush. Or better yet they could go underground to avoid the rushing wave, deploy the scuba gear, and then swim to the top after the water has distributed and debris/cars/houses/trees have settled down. You would have to take into effect any pressure changes I suppose, to where if you were underground shielded from the wave, you might still be crushed by the force of water rushing in but that seems fairly easy to accommodate though.

Glad I was able to watch this on Netflix before they take it away, and obviously it got the wheels turning :)