A seismic scale is used to measure and compare the severity of earthquakes. An earthquake is the result of a sudden release of energy in the Earth 's crust that creates Seismic waves Earthquakes are recorded with a Seismometer

Two fundamentally different but equally important types of scales are commonly used by seismologists to describe earthquakes. The original force or energy of an earthquake is measured on a magnitude scale, while the intensity of shaking occurring at any given point on the Earth's surface is measured on an intensity scale.

See the table of seismic scales at the end of this article.

The severity of an earthquake is described by both magnitude and intensity. These two frequently-confused terms refer to different, but related, observations. Magnitude, usually expressed as an Arabic numeral, characterizes the size of an earthquake by measuring indirectly the energy released. The arabic numerals (often capitalized are the ten Digits (0 1 2 3 4 5 6 7 8 9 which—along with the system By contrast, intensity indicates the local effects and potential for damage produced by an earthquake on the Earth's surface as it affects humans, animals, structures, and natural objects such as bodies of water. A body of water is any significant accumulation of Water, usually covering the Earth or another planet Intensities are usually expressed in Roman numerals, and represent the severity of the shaking resulting from an earthquake. Roman numerals are a Numeral system originating in ancient Rome, adapted from Etruscan numerals. Ideally, any given earthquake can be described by only one magnitude, but many intensities since the earthquake effects vary with circumstances such as distance from the epicenter and local soil conditions. The epicenter or epicentre is the point on the Earth 's surface that is directly above the Hypocenter or focus the point where an Earthquake In practise, the same earthquake might have magnitude estimates typically differing by few tenths of a unit, depending on which magnitude scale is used and which data are included in the analysis.

## Seismic intensity scales

The first simple classification of earthquake intensity was devised by Domenico Pignataro in the 1780s. However, the first recognisable intensity scale in the modern sense of the word was drawn up by P. N. G. Egen in 1828; it was ahead of its time. The first widely adopted intensity scale, the Rossi-Forel scale, was introduced in the late 19th century. The Rossi-Forel scale was one of the first seismic scales to reflect earthquake intensities Since then numerous intensity scales have been developed and are used in different parts of the world: the scale currently used in the United States is the Modified Mercalli scale (MM), while the European Macroseismic Scale is used in Europe, the Shindo scale is used in Japan, and the MSK-64 scale is used in India, Israel, Russia and throughout the CIS. The Mercalli intensity scale is a scale used for measuring the intensity of an Earthquake. The European Macroseismic Scale (EMS is the basis for evaluation of seismic intensity in European countries and moreover in use on most other continents The European Union ( EU) is a political and economic union of twenty-seven member states, located primarily in The Japan Meteorological Agency seismic intensity scale is a measure used in Japan and Taiwan to indicate the strength of Earthquakes It is measured in units of. For a topic outline on this subject see List of basic Japan topics. The Medvedev-Sponheuer-Karnik scale, also known as the MSK or MSK-64, is a macroseismic intensity scale used to evaluate the severity of ground shaking on the basis India, officially the Republic of India (भारत गणराज्य inc-Latn Bhārat Gaṇarājya; see also other Indian languages) is a country For a topic outline on this subject see List of basic Israel topics. Russia (Россия Rossiya) or the Russian Federation ( Rossiyskaya Federatsiya) is a transcontinental Country extending Most of these scales have twelve degrees of intensity, which are roughly equivalent to one another in values but vary in the degree of sophistication employed in their formulation.

## Magnitude scales

The first attempt to qualitatively define a single, absolute value to describe the size of earthquakes was the magnitude scale (the name being taking from similarly formulated scales used to represent the brightness of stars).

### Local magnitude scale

The local magnitude scale (ML), also popularly known as the Richter Scale, is a quantitative logarithmic scale. The Richter magnitude scale, or more correctly local magnitude M L scale assigns a single number to quantify the amount of seismic energy released In the 1930s, California seismologist Charles F. Richter devised a simple numerical scale to describe the relative sizes of earthquakes in Southern California. The 1930s were described as an abrupt shift to more radical and conservative lifestyles as countries were struggling to find a solution to the Great Depression. Charles Francis Richter ( April 26, 1900 &ndash September 30, 1985) was an American seismologist and physicist The name "Richter Scale" was coined by journalists and is not generally used by seismologists in technical literature. The Richter magnitude scale, or more correctly local magnitude M L scale assigns a single number to quantify the amount of seismic energy released ML is obtained by measuring the maximum amplitude of a recording on a Wood-Anderson torsion seismometer (or one calibrated to it) at a distance of 600 km from the earthquake. Seismometers (from Greek Seism - "the shakes" - and Metro - "I measure" are instruments that measure and record motions of the ground including Other more recent magnitude measurements include: body wave magnitude (mb), surface wave magnitude (Ms), and duration magnitude (MD). Body wave magnitude (mb is a way of determining the size of an Earthquake, using the amplitude of the initial P-wave to calculate the magnitude The Surface wave magnitude ( MS) is one of the magnitude scales used in Seismology to measure the "size" of an Earthquake Each of these is scaled to give values similar to those given by the local magnitude scale; but because each is based on a measurement of one aspect of the seismogram, they do not always capture the overall power of the source. A seismogram is a graph output by a Seismograph. It is a record of the ground motion at a measuring station Specifically, some can be affected by saturation at higher magnitude values—meaning that they systematically underestimate the magnitude of larger events. This problem sets in at around magnitude 6 for local magnitude; surface-wave magnitude saturates above 8. Despite the limitations of older magnitude scales, they are still in wide use, as they can be calculated rapidly, catalogues of them dating back many years are available, they are sufficient for the vast majority of observed events, and the public is familiar with them.

### Moment magnitude scale

Because of the limitations of the magnitude scales, a new, more uniformly applicable extension of them, known as moment magnitude (MW) scale for representing the size of earthquakes, was introduced by Hiroo Kanamori in 1977. TalkMoment magnitude scale#Real world examples please.--> The moment magnitude scale Hiroo Kanamori (金森 博雄 Kanamori Hiroo; October 17, 1936 — is a Japanese Seismologist who has made fundamental contributions In particular, for very large earthquakes moment magnitude gives the most reliable estimate of earthquake size. This is because seismic moment is derived from the concept of moment in physics and therefore provides clues to the physical size of an earthquake—the size of fault rupture and accompanying slip displacement — as well as the amount of energy released. In Physics, the moment of force (often just moment, though there are other quantities of that name such as Moment of inertia) is a Pseudovector So while seismic moment, too, is calculated from seismograms, it can also be obtained by working backwards from geologic estimates of the size of the fault rupture and displacement. A seismogram is a graph output by a Seismograph. It is a record of the ground motion at a measuring station The values of moments for observed earthquakes ranges over more than 15 orders of magnitude, and because they are not influenced by variables such as local circumstances, the results obtained make it easy to objectively compare the sizes of different earthquakes.