2011 Tōhoku earthquake and tsunami for the event was based on a calculation that requires only about 3 minutes. This calculation is, in turn, based on the maximum amplitude of the seismic wave. The amplitude of the seismic wave is measured using the , which is similar to Richter magnitude scale. However, these scales "saturate" for earthquakes that are above a certain magnitude (magnitude 8 on the JMA scale); that is, in the case of very large earthquakes, the scales' values change little despite large differences in the earthquakes' energy. This resulted in an underestimation of the tsunami's height in initial reports. Problems in issuing
Absolute magnitude using an absolute magnitude, one must specify the type of electromagnetic radiation being measured. When referring to total energy output, the proper term is bolometric magnitude. The bolometric magnitude usually is computed from the visual magnitude plus a bolometric correction, . This correction is needed because very hot stars radiate mostly ultraviolet radiation, whereas very cool stars radiate mostly infrared radiation (see Planck's law). Some stars visible to the naked eye have such a low absolute magnitude that they would appear bright enough to outshine the planets and cast shadows if they were at 10 parsecs from the Earth. Examples