Mercalli intensity scale Mercalli intensity scale The Mercalli intensity scale is a seismic intensity scale used for measuring the intensity of an earthquake. It measures the "effects" of an earthquake. It is distinct from the moment magnitude ("M") usually reported for an earthquake, which is a measure of the "energy" released (sometimes misreported as the Richter magnitude, "M"). The intensity of an earthquake is not entirely determined by its magnitude. It is not based on first physical principles, but is, instead, empirically based on observed effects. The Mercalli scale quantifies the effects of an earthquake on the Earth's surface, humans, objects of nature,
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