world's most active earthquake belt
Pacific Ring of Fire (Not actually on fire)
Japan is spread across four tectonic plates, the Pacific plate, the Philippine plate, the North American plate and the Eurasian plate. The Japanese Islands are situated in a subduction zone in the northwestern margin of the Pacific Ocean where the Pacific Plate and Philippine Sea Plate are subducting.
The four plates
Nishiwaki, Hirotoshi "Introduction to the Landforms and Geology of Japan" 2009 http://www.glgarcs.net/
Keller, Edward A. DeVecchio, Duane E. Natural Hazards:New Jersey. Pretence Hall, 2012. Thired Edition

