Natural disasters in Japan shaking we call an earthquake. Earthquakes can cause shaking that could last seconds or minutes. Besides that, there may be several earthquakes over a period ranging from hours to weeks called aftershocks, and the magnitude of the following tremors will decrease with time. It is important to know the earthquake magnitude because it can be the clue if there will be any aftershocks. Because of that, magnitude can be measured on the Richter scale, invented by Charles F. Richter in 1934. The Richter magnitude is calculated from the amplitude of the largest seismic wave recorded for the earthquake. In the
Absolute magnitude Absolute magnitude Absolute magnitude is a measure of the luminosity of a celestial object, on a logarithmic astronomical magnitude scale. An object's absolute magnitude is defined to be equal to the apparent magnitude that the object would have if it were viewed from a distance of exactly 10 parsecs (32.6 light-years), with no extinction (or dimming) of its light due to absorption by interstellar dust particles. By hypothetically placing all objects at a standard reference distance from the observer, their luminosities can be directly compared on a magnitude scale. As with all astronomical magnitudes, the absolute magnitude can be specified