Seismicity of The Earth: The largest seismic movements are associated with tectonic shifts of continental plates that make up the Earth's crust. They are clearly shown in this ultimate physical map of seismic activity as first best measured over two decades from 1960 through 1980. Today's seismology instruments can measure hundreds of distinct earthquakes within just one square mile. For those who love seeing below the surface of this living planet, this "Seismicity of The Earth" map will stir their world.