What If Could we survive the dinosaur-killing asteroid?

[Kyng]

66 million years ago, an asteroid struck near the Yucatán Peninsula in Mexico, wiping out all the dinosaurs (well, except the birds ). But, if a similar asteroid were to strike today, could humanity survive it? The above video, by YouTube user melodysheep, explores several versions of this scenario:

• Scenario 1 - A strike without warning: Central American and the southern United States are vaporised by the blast (so, the 100 million people living here would die within seconds). Then, magnitude 11 earthquakes would run across the Earth, and tsunamis would flood up to 100km inland, drowning over 3 billion people. Next, molten lava would rain down from the sky - although some people could survive by quickly retreating into fallout shelters (or perhaps mines or subways). All told, perhaps around 2 billion people (25% of Earth's population) could survive the initial effects of the blast.
  
  However, fiery debris and acid rain would fall from the sky for years after the impact. Thus, farming (or any other open-air activity) would be deadly. And most of those shelters would quickly run out of food. Only a small number of doomsday bunkers would remain hospitable in the long term, housing world governments and the ultra-rich. But even a small number people without access to these could survive - for example, by harvesting fungi, which don't rely on sunlight. Nevertheless, even if there were a few scattered survivors, humanity would be a pale shadow of its current self.
  
  
• Scenario 2 - Moving Mountains: So, what if we did know about the asteroid in advance? Well, we could try deflecting it: in 2022, the Double Asteroid Redirection Test (DART) succeeded at deflecting a small asteroid. But the dinosaur-killer was much larger: it was 10km across. If we tried to deflect it, we'd run the risk of breaking it into smaller, equally-deadly pieces.
  
  Other possible methods include using high explosives, lasers, or solar sails to deflect the asteroid into a new trajectory. But, what if all of these failed? Well, we'd need a backup plan...
  
  
• Scenario 3 - The Grand Plan: We'd start by evacuating the areas around the Yucatán Peninsula (so, Bugs Bunny might actually have a use, for once ). Then, we'd construct a series of heavily-armoured, self-sustaining habitats, designed to withstand raining meteorites and severe earthquakes. For example, mines and subway tunnels could be repurposed into underground cities, with their own nuclear reactors and vertical farms (plus algae farming). Fortified seed vaults could be created - and water reservoirs could be built to save water from acid rain contamination.
  
  Of course, it's unlikely that we could save absolutely everyone - but the subways should, at least, be able to save around 1 billion people. But if all else fails, there'd be one last option:
  
  
• Scenario 4 - Leave Earth entirely: A chosen few could form a small colony on the Moon, and watch disaster unfold from there. Yeah, this wouldn't save many lives, but it is possible .

Fortunately, all asteroids larger than 1km within the Solar System have been mapped - so, even if there was one aimed at Earth, it's practically certain that we'd have a large amount of warning. That pretty much rules out Scenario #1 - but I am rather hoping we don't have to do #3 either. Instead #2 seems like the way to go!

So, do you have any thoughts yourself?