Condition: The event must happen in minutes
Impossible. Really, it's impossible. Consider an earthquake, for which minutes is a very, very long time. It flattens buildings. An earthquake lasting minutes would flatten cities. The destruction of the world in just minutes would flatten literally everything. Worse, it would churn everything into dirt soup. Considering how much mass is involved, your explorer would be lucky to find a brick, much less any other kind of proof of civilization.
But, maybe... if we change the timeline to weeks or months...
An impact won't work, that means no surface explosion of any kind. Too fast, too violent, probably won't leave the Earth in its current orbit, and the energy sufficient to split it up would spread it all over the place. So, no impact.
But... what if the core started to expand? Slowly...
There will be destruction. After all, the mantle is sitting atop a molten soup of fluid and even the most even expansion will cause uneven results. Everything from volcanoes to calderas would erupt. But if it happens slowly enough, it might not be terrestrially devastating.
So, let's consider something along the lines of the movie The Core. In that movie, the theoretical threat of an enemy state weaponizing earthquakes led the U.S. to develop Project Destini (Deep Earth Seismic Trigger INItiative), a tool that would (theoretically) produce focused earthquakes anywhere on the globe.
Except that when they tried it, it stopped the core from spinning. No magnetic field. Birds can no longer navigate. Pacemakers stop. Dogs and cats... living together! Mass hysteria! (Whoops, mixing my movies... sorry.)
What if the nations of your Earth were doing the same thing? Maybe they were simply trying to probe the core and the "probe" exploded, causing the core to expand. The planet's honking big! So such an effect would take time.
And time is what you want (sorry). It takes time to gently rip the Earth apart — but only so much! Because you want those chunks (similar to what was seen in season 5 of Agents of S.H.E.I.L.D..) to gently stay put, both in orbit and generally in locale, such that your explorer can swoop around in between chunks.
Remember, there's a LOT of planet to deal with
A huge part of your problem is that 99.99% of the Earth is everything except the surface. What you have in mind seems like it would be huge — but compared to the rest of the planet it's insignificant. It would actually be really, really hard for your adventurer to find chunks with buildings on them. But that's great! Because you want the process to take years.
"Realistically" the localized asteroid belt once known as the Earth would be a bunch of chunks floating around, hitting one another, and causing a ton of grief. Most of it would be metal, not rock (I think, the outer core might be mostly rock, so maybe it will be mostly rock...). An no matter how gently it was expanded into chunks, some of those chunks would eventually come into contact with the Moon. Now we have the proverbial toilet brush whisking chunks of the Earth around like a whirlpool.
Actually, now that I think about it, the effect would be pretty cool. The Moon would act somewhat like the guardian satellites that help shepherd the rings of Saturn. The math might not work out... but the concept of a moon-shepherded whirlpool in space is cool beyond reason.
On the other hand, what you could also end up with is the surface (mantle) of the Earth broken up and orbiting the swollen-and-now-cooling core. A new, mostly metal (maybe) planet having almost exactly the original mass but now surrounded by a ring system that happens to be made up of fairly large chunks. Astronomically, they'd eventually plunge back to the planet's surface. But that could take a while. A long while.
But, in the end, you'd have the effect you want... so long as you don't want atmosphere
So, we slowly expand the core like a swelling appendicitis until the either the surface breaks up and floats away or the entire planet breaks up. It's slow, because that's the only hope any building has of surviving.
The result is either a new planet with a ring system containing the chunks you're looking for or a localized asteroid field made up of the mass of the planet that eventually becomes this whomping cool whirlpool shepherded by Luna, the Guardian Moon.
What you do NOT have is atmosphere. Anywhere. There's no way to keep it around the chunks in any circumstance. The buildings and desiccated human remains are in a complete vacuum and might not be protected any longer even by the Van Allen Radiation Belt. (A curious thought, that, but I'll leave it to another to analyze.)