The USArray's seismographs are closely spaced in a grid pattern with unprecedented density, clearly showing how seismic waves travel outward from an earthquake's epicenter in all directions.

Each circle on the map represents one seismograph. The color of each circle represents the amplitude, or height, of the earthquake wave detected. Blue represents downward ground motion, red represents upward ground motion, and darker colors indicate larger amplitudes. This is the actual data from the instruments.