A translation and detailed prefectural links lie beneath.
View Earthquake Danger Zones fullscreen
This link breaks down the above image into detailed views of each prefecture (all in Japanese).
the above is not a map of where most earthquakes happen, rather a description of the structure of the land and how that will modify the intensity for people in those areas. The text below the image briefly talks about soil types and how that affects the seismic intensity. The key shows how much more severe an earthquake would be in each of the coloured areas.