While a recent report by CNN discusses whether this is actually an uncommon occurrence or not, it clearly shows how Hashem is directing these earthquakes to affect population centers, not the oceans they usually hit.
"Natural processes become disasters only when they interact with people," said Seth Stein, a distinguished faculty member at Northwestern University in Evanston, Illinois.Apparently Hashem wants us to take note. To paraphrase the saying - if a 7.7 earthquake rattles the Atlantic, does anyone make Teshuva?
Misfortune only comes to the world for the Jewish people [to make them do Teshuva].
The Jewish People will only be redeemed through Teshuva (RaMBa"M).