Collapse began on November 3, 2019, in Washington, D.C., USA. Basically, a building spontaneously collapsed. And then another, and then three more, etc, etc. Then it spread out to other cities from there. No one really had time then to get their heads around it, though there were plenty of heroic efforts in that direction. Not much about it makes sense. The "effect" - for lack of a better term - progressed in a quasi-random dispersion pattern, but space-filled. Meaning, what got hit at first wasn't predictable, but the overall spread was predictable, and it eventually went everywhere.
Eventual detailed examination of Collapsed materials showed the damage was uniformly due to micro-scale "stress fractures" - even in A) parts not under the largest stress and B) materials that just don't fracture that way. The effect seemed to scale downward gradually - the largest buildings were more likely to go first. But it's not just a matter of size, it's density too - a normal 4-door car, by itself, seems to be largely immune to Collapse. But as you may have noticed if you've walked any of the congestion-of-death roads near large cities, where a bunch of cars were close together, they eventually got hit too. One thing I want to stress here, is that, like Infection, Collapse is still happening. Even new structures built from completely post-Collapse materials (cutting down trees, forging your own nails, etc.) have been hit.
Based on the original spread pattern - when the global media was still running and avidly following its own demise - its assumed it spreads physically somehow...for example, mountains and rivers seemed to not matter at all, and the oceans and poles slowed it only slightly. From the remains of the old net records, by November 7th it had hit even the most remote islands and outposts. It's unclear if the effect takes time to build or if it is *localized*, but one or more of those must be true, as there is often a delay before Collapse hits a new structure - it is inversely correlated to size, but only vaguely. No one has managed to catch it happening under a microscope, either - it's like the proverbial watched pot, only instead of boiling, it wants to sneak off and wreck all your shit.
The most reliable way appears to be the Sherlock Holmes "dog did not bark" method - find a structure that's still standing, and move in. If it's still standing now, it's a decent bet that Collapse is giving it a pass for some reason. Fortify it as needed, but do *not* add expansions - you never know when you'll cross that line and get put on Santa's Naughty List. No particular materials seem to be immune to the effect - wood, metal, concrete, plastic, carbon-fiber, it all goes down.
Natural caves seem ok. Also living material - living trees, no matter how large, do not seem to get hit, though treehouses *in* them *have*. At least one guy has a froofy eco-house built in the 70's over a decade by forcing trees to grow in the right shape, but it's fairly isolated and small, so not sure there. Fortified caves are risky too - I've seen pics from Kevin's hike over to Cheyenne Mountain (for some reason he thought that they'd let him in rather than shoot him to death). He got lucky, though they didn't - both the north and the south portal were collapsed. He managed to crawl through and get to the blast doors, which were lying there in three pieces. There weren't any Infected in there, but there was more Collapse inside and everyone left was dead - he was getting light-headed and bugged out - we assume collapse fucked their power and all the air handlers went down. This place was essentially a cave (though a non-natural one), with only two exposures, 29' x 22' and 15' x 17'. So fortifying a cave entrance *may* still get hit, depending on the size - smaller is presumed to be better, and if you can fortify it with large natural stones, better yet.
You can get a moderate number of modern tents together if you don't clump them too tightly, and they're not retarded super-tents. Even if a tent does Collapse though, duct tape and 15 minutes pretty much solves that problem in the short-term.
Most mobile homes and RV's seem to be ok *by themselves*, but if you get them too close to other stuff, wave goodbye.
Civilization was just starting to pull itself back up off the ground from the sucker-punch that was Infection when the crazy-ex-girlfriend of Collapse leapt onto its back and started eye-gouging. There's a lot of speculation on the reasons for all this, including Infection, but no good info. Infection seems to have originated in both the US and China relatively simultaneously, whereas Collapse clearly spread from Washington D.C. - but does that imply the US government caused it (and why?), or that it was an outside attack? We've got nothing. There's been no suspiciously-immune invading army, foreign, alien or extra-dimensional. No terrorist group claimed responsibility (though it's possible things did not go quite as they had planned). No one appears to have come out of this whole thing particularly well - except for rats, but the sole surviving NIMH guy has assured me that they're completely normal.