My theory is that in the new version of reality Jake created, something prevented Roland from being able to stop the fall of the Tower, and that the earthquakes are part of the process of the fabric of reality ripping itself apart. Mr. King has said that he intentionally didn't link the two stories (11/22/63 and The Dark Tower), but I'm not buying it, personally.
I thought it was down to the butterfly effect,and also by saving JFK the Vietnam war didn't happen and time being obdurate the non loss of life had to be made up somewhere.Hence all the deaths from earthquakes
I thought of the timeline as a string stretching from the beginning to the end of time.
You are at a point along the string which is 2013. If youu go back in time, the green-yellow-red card man has to 'save' the time so you can go back. Sort of like tying the string around a peg. The more you change things in the past, the harder it is for the green-yellow-red card man to keep the string on the peg.
Jake changed the past and the string popped of the peg causing the earthquakes. Jake returned to a future that wasn't 'his' future since the string had moved.
When he returned to the past, the new orange-card man was able to put the string back on the proper peg.
roland-shmoland...there was ample, and easy opportunity for king to tie in anything he wanted...he doesn't need, at this late stage, to get all hocusy-pocusy about it...like we'd all be fooled !!
of course, why, after saying before that everything in every book is connected, he did not...that's another conspiracy theory, right ?
didn't portal boy say something like each trip is not a complete reset..and each trip that changed things twisted life, the universe and everything more and more...and some trips twisted it all the hades...and who knew what might happen when it got twisted too much...(now we might have a clue !)
what if...'11/22/63' is to 'the dark tower' what 'the regulators' is to 'desperation'