There are bugged pets that still cause unintended effects like screwed up sound files and tremors.
I trained some random elite turtle a few weeks ago that was bugged in this way.
It's always possible that it is "something", but this is quite a bit different from how the Cataclysm event played out. It is true that people dismissed the early Earhquakes before Cataclysm, but a LOT of people were saying they'd seen them. This time it has been relatively few people, and people have been "noticing" these "earthquakes" for months and months.
So unless Blizzard has been running a pre-expansion event for almost two years (since before Mists)--It's nothing more than various effects caused by pets, items like the racer, etc.
Not to mention that, as has been pointed out above, this would mean them repeating the exact same pre-expansion event as Cataclysms. Which I can't imagine they'd do since, one, people get angry about the effort in expansion events, and it seems logical they'd put a lot of work into the next one... and two, the most likely expansions are Legion-related (Legion come from the sky, not below the earth) or Azshara-related (Naga come from the sea, not below the earth). A more likely event is a carefully implemented increase in the amount of rain and thunder storms in all zones.