Seismic magnitude scales the International Association of Seismology and Physics of the Earth's Interior (IASPEI) has standardized the measurement procedures and equations for the principal magnitude scales, , , , and . The first scale for measuring earthquake magnitudes, developed in 1935 by Charles F. Richter and popularly known as the "Richter" scale, is actually the , label ML or M. Richter established two features now common to all magnitude scales. First, the scale is logarithmic, so that each unit represents a ten-fold increase in the "amplitude" of the seismic waves. As the energy of a wave is 10 times its amplitude, each
Apparent magnitude brightness of sources at ultraviolet, visible, and infrared wavelengths. An apparent magnitude is usually measured in a specific passband corresponding to some photometric system such as the UBV system. In standard astronomical notation, an apparent magnitude in the V ("visual") filter band would be denoted either as "m" or often simply as "V", as in ""m" = 15" or ""V" = 15" to describe a 15th-magnitude object. The scale used to indicate magnitude originates in the Hellenistic practice of dividing stars visible to the naked eye into six "magnitudes". The brightest stars in the night sky were said to be