I believe we STILL haven't heard of this.
You have now.
http://www.freerepublic.com/focus/f-news/1146624/posts
I stand corrected on Hoagland's first name. As regards his stuff, I am neither a reflexive skeptic or true believer. Such matters as he investigates ought to have nothing to do with 'belief', only with evidence and investigation. He seems to see anomalous things as 'alien architecture', rather than 'what the hell is that' and 'what ELSE could it be'. In spite of this however, I appreciate that there are people looking for that kind of stuff. I haven't personally explored the surfaces of the Moon and Mars, so I can't say that it is free of someone else's garbage. I suspect that there isn't anything there, but I don't absolutely know that. You won't hear me call him or Friedman 'crackpots'. I just think that they're a little bit predisposed towards certain conclusions, which they also happen to be making a living off of.
Speaking of 'burrows', where exactly does the notion come from, apart from movies like 'Deep Impact', that one would be any safer underground?
This isn't just a 'bigger nuclear strike'. Personally, I'd just as soon take my chances on a bald hilltop on very high ground, rather than deal with the massive ground shock wave that's ring the Earth like a bell and possibly collapse even reinforced subterranean structures.
What we'd be looking at is an event that is part massive earthquake, part Tsunami, part falling debris and part atmospheric occlusion.
Ideally, I'd be in the mountains somewhere above the possibility of any seismic wave threat, and near the mouth of a cave in case debris starts falling out of the sky. I would in no case go farther into the cave than I could dig myself out of, should a collapse occur.
Having overhead cover is probably a really good idea. Being way underground, might not be.
I don't think that there's anything to this, at this time. It will happen eventually. It has many times in the past.
It makes for an interesting intellectual exercise though.
Suppose you're the President. You have been briefed that such an event is going to take place. When do you notify the public, or do you, at all? You can't possibly shelter them all. Is there a benefit to the public from notifying them? What are most people going to do with that warning, besides jump in their cars with the family pictures a day or two before 'impact day' and try to drive somewhere, making the roads useless to all?
On the other hand, the object is going to become public knowledge before it strikes. It isn't going to sneak up on us. Withholding such knowledge would be disatrous for not just a particular government, but for the concept of government.