Why earthquakes are more common in Japan?

Japan has a lot of earthquakes because there's this giant catfish curled up under the islands and when it moves, earthquakes happen... NO, of course not, but that's an old Japanese myth.

The real reason why Japan has so many earthquakes is because of where it is on the globe.  Japan sits on an area where two tectonic plates meet.  Tectonic plates are, of course, the plates on which the earth's continents and oceans sit.  The plates float on the molten rock below.  When they move, earthquakes can happen.

Japan is on the place where the North American plate and the Eurasian plate meet.  It is also near to the Philippine and Pacific plates.  The first two are more important because they meet right under Honshu -- the main island of Japan.