Is there any other kind?
...insane luddite religion...Plate movement occurs because subduction and gravitational gradient forces act continuously over extended periods of time. An explosion, on the other hand, is a brief "impulse force". So yes, an explosion could cause localized shifts along fault lines where pressure builds up. But it couldn't drive large-scale movement of an entire plate.
Yes plate shifts happen over time naturally, but a powerful enough explosion could assumedly cause a rapid shift.
But these details aren't important anyway. The volcanoes and earthquakes are scary enough. The physics behind them isn't really an issue in the story.
In any event, I'm eager to read your next iteration. It's getting interesting.
I just sat through the Avengers, if I have to suspend my disbelief about a metal that creates antiprotons and yet isn't wreathed in constant explosions. Then you can suspend your disbelief for that!
...though there's no chance of there being any survivors seeing as the game is set 100-150 years post catastrophy.
The woman you see could be the daughter of the original character, who survived? You could add in some photo in her house that shows the two together "back in the days", perhaps (and you see that they are very look-alike, same haircut and stuff), or some other clue.
Took the thoughts right out of my head, I'm sure when Will reads your idea though he'll jump straight to SHE'S A CLONE! LOL!
And now the laptop battery dies, so I'll finish this post now.