Map of historic seismicity, major faults, and paleoseismic summary of San Andreas Fault system. On the Richter scale, the magnitude of an earthquake is related to the released energy E in joules (J) by the equation. (The 1906 San Francisco earthquake, for example, had a Richter magnitude of 8.25.) After an unparalleled success in scientific and practical applications the magnitude is developing into a concept with a clearer physical meaning and a more solid theoretical foundation. All magnitude scales should yield approximately the same value for any given earthquake. (The 1906 San Francisco earthquake, for example, had a Richter magnitude of 8.25.) A special case is the Seismicity of the Earth catalog of Gutenberg & Richter (1954). [62] (Not to be confused with the height of a tidal wave, or run-up, which is an intensity effect controlled by local topography.) It is "approximately related to the released seismic energy. First, the scale is logarithmic, so that each unit represents a ten-fold increase in the amplitude of the seismic waves. Each is valid for a particular frequency range and type of seismic signal. The magnitude determined from the maximum particle amplitude or velocity reflects the maximum … The Richter scale measures the magnitude of an earthquake (how powerful it is). The moment is then converted into a number similar to other earthquake magnitudes by a standard formula. Magnitude scales , like the moment magnitude, measure the size of the earthquake at its source. [11] Richter established two features now common to all magnitude scales. Representative shocks of various magnitudes are discussed. After Richter (1935), various magnitude scales are proposed; all these scales are discussed below. Magnitude is determined using the logarithm of the amplitude (height) of the largest seismic wave calibrated to a scale by a seismograph. Richter used seismograms of earthquakes that occurred in the San Andreas fault zone to calibrate his magnitude scale. Adaptation to local conditions has led to various regional K scales, such as KF and KS. The moment magnitude provides an estimate of earthquake size that is valid over the complete range of magnitudes, a characteristic that was lacking in other magnitude scales. This happens because the relation between the seismic measurements and the... For earthquakes that occurred between about 1890 (when modern seismographs came into use) and 1935 when Charles Richter developed the magnitude scale, people went back to the old records and compared the seismograms from those days with similar records for later earthquakes. [6] Determination of an earthquake's magnitude generally involves identifying specific kinds of these waves on a seismogram, and then measuring one or more characteristics of a wave, such as its timing, orientation, amplitude, frequency, or duration. An earthquake at the same distance that made a displacement of 10 mm was a magnitude 2, 100 mm was magnitude 3, and so on. It is relatively easy to acquire the necessary materials and build your own seismometer. For earthquakes prior to about 1890, magnitudes have been estimated by... United States Geological Survey (USGS) Natural Hazards Response; 2012; FS; 2012-3061; Lamb, Rynn; Jones, Brenda K. The Global Seismographic Network; 2011; FS; 2011-3021; Gee, Lind S.; Leith, William S. Earthquake Hazards - A National Threat; 2006; FS; 2006-3016; USGS Science Helps Build Safer Communities; Geological Survey (U.S.), ANSS-Advanced National Seismic System; 2000; FS; 075-00; Benz, Harley M.; Filson, John; Arabasz, Walter; Gee, Lind; Wald, Lisa. The rate of earthquakes began to increase starting around 2009 and accelerated in 2013-2014. This is why, in the 1989 Loma Prieta earthquake, the Marina district of San Francisco was one of the most damaged areas, though it was nearly 100 km from the epicenter. The Richter magnitude scale, also known as the local magnitude (M) scale, assigns a number to quantify the amount of seismic energy released by an earthquake. Teleseismic Magnitude Scales To study earthquakes outside southern California, Richter extended the concepts of his local magnitude scale for global application. Preview; This is what was to eventually become known as the Richter magnitude. This indicates how strong in your memory this concept is. Richter Magnitude (or Local Magnitude) ML Richter (1935) defined the local magnitude ML of an earthquake observed at a station to be ML = log A - log Ao ( ∆) (1) This results in systematic underestimation of magnitude in certain cases, a condition called saturation. [31] As originally defined by Gutenberg (1945c) mb was based on the maximum amplitude of waves in the first 10 seconds or more. [60] The tsunami magnitude scale, Mt, is based on a correlation by Katsuyuki Abe of earthquake seismic moment (M0 ) with the amplitude of tsunami waves as measured by tidal gauges. This was a large urn on the outside of which were eight dragon heads facing the eight principal directions of the compass. The magnitude does not depend on where the measurement is made. While the recommended label for magnitudes derived in this way is M0(An),[71] the more commonly seen label is Mfa. The 1906 San Francisco earthquake registered 8.2 on the Richter scale. But what does this scale really mean? In particular, for very large earthquakes, moment magnitude gives the most reliable estimate of earthquake size. When an earthquake occurs, it... Earthquakes are recorded by a seismographic network . A similar effect channeled seismic waves between the other major faults in the area.[5]. "Smaller" earthquakes closer to the lab or "larger" earthquakes more distant might produce the same peak amplitude, so the formula includes a distance correction for earthquakes not at the standard distance. This indicates how strong in your memory this concept is. In this area the ML scale gives anomalous results for earthquakes which by other measures seemed equivalent to quakes in California. Different magnitude scales are necessary because of differences in earthquakes, the information available, and the purposes for which the magnitudes are used. These are distinguished from seismic intensity scales that categorize the intensity or severity of ground shaking (quaking) caused by an earthquake at a given location. When an earthquake occurs, one of the first questions is "where was it?" [28], The mb or mb scale (lowercase "m" and "b") is similar to mB , but uses only P-waves measured in the first few seconds on a specific model of short-period seismograph. K (from the Russian word класс, "class", in the sense of a category[56]) is a measure of earthquake magnitude in the energy class or K-class system, developed in 1955 by Soviet seismologists in the remote Garm (Tadjikistan) region of Central Asia; in revised form it is still used for local and regional quakes in many states formerly aligned with the Soviet Union (including Cuba). Professor Charles Richter of California Institute of Technology proposed a scale of earthquake magnitude in 1935 to indicate the quantity of energy released by a single earthquake. [65], Mc scales usually measure the duration or amplitude of a part of the seismic wave, the coda. Even for distant earthquakes, measuring the duration of the shaking (as well as the amplitude) provides a better measure of the earthquake's total energy. M w magnitude scale, is therefore regarded … Because of the limitations of all three magnitude scales (ML, Mb, and Ms), a new, more uniformly applicable extension of the magnitude scale, known as moment magnitude, or Mw, was developed. Earth Resources Observation and Science (EROS) Center, Earth Resources Observation and Science Center, Updated USGS Earthquake Monitoring Strategy Released, A 100-year-long History of Earthquakes and Seismic Monitoring in Hawaii, Recovery Act Funds Will Upgrade Earthquake Monitoring, Region 2: South Atlantic-Gulf (Includes Puerto Rico and the U.S. Virgin Islands), Cumulative number of earthquakes with a magnitude of 3.0 or larger in the central and eastern United States, 1973-2014. But within their limits, these two scales are a reliable gauge of the actual energy that earthquakes release. Seismic moment is considered the most objective measure of an earthquake's "size" in regard of total energy. Any skew in the spectral distribution can result in larger, or smaller, tsunamis than expected for a nominal magnitude. Seismic magnitude scales are used to describe the overall strength or "size" of an earthquake. [73], Peak ground velocity (PGV) and Peak ground acceleration (PGA) are measures of the force that causes destructive ground shaking. Here s what earthquake magnitudes mean earthquake magnitude scales the nature of earthquake ground motion earthquake signal sensing terms you need to know about earthquakes. The primary goal of U.S. Geological Survey (USGS) Natural Hazards Response is to ensure that the disaster response community has access to timely, accurate, and relevant geospatial products, imagery, and services during and after an emergency event. Nuttli resolved this by measuring the amplitude of short-period (~1 sec.) In the 1977–1991 period 1977–1991 period to ensure an homogeneous database. MEMORY METER. These may be labelled "ML", or with a lowercase "l", either Ml, or Ml. Md designates various scales that estimate magnitude from the duration or length of some part of the seismic wave-train. K values in the range of 12 to 15 correspond approximately to M 4.5 to 6. is a Philippine national institution dedicated to provide information on the activities of volcanoes, earthquakes, and tsunamis, as well as other specialized information and services primarily for the protection of life and property and in support of economic, productivity, and sustainable development. Earthquake magnitude is a measure of the size of the earthquake reflecting the elastic energy released by the earthquake. Notably, it measured the amplitude of surface waves (which generally produce the largest amplitudes) for a period of "about 20 seconds". Back then, it was said to be magnitude 8.5, but today we say it was 9.5. [49] However, it is based on a simple model of rupture, and on certain simplifying assumptions; it incorrectly assumes that the proportion of energy radiated as seismic waves is the same for all earthquakes. Richter scale, widely used quantitative measure of an earthquake’s magnitude (size), devised in 1935 by American seismologists Charles F. Richter and Beno Gutenberg. Unfortunately, Earth is not transparent and we can't just see or photograph the earthquake disturbance like meteorologists can photograph clouds. What was the first instrument that actually recorded an earthquake? "[80] Further study has found that most of the MGR magnitudes "are basically Ms for large shocks shallower than 40 km, but are basically mB for large shocks at depths of 40–60 km. This map shows earthquakes above magnitude 4.0 in the eastern United States since 1973, the first year with a complete catalog. The Richter scale, officially called the "Richter Magnitude Scale," is a numerical value used to measure the power of earthquakes.It is a logarithmic scale based on the amplitude of waves recorded by a seismograph. Interactive map showing earthquake scenario data. Practice. The first earthquake magnitude scales were simple designations such as major/minor. Where the details of how a magnitude has been determined are unknown, catalogs will specify the scale as unknown (variously Unk, Ukn, or UK). How can an earthquake have a negative magnitude? As more seismograph stations were installed around the world, it became apparent that the method developed by Richter was strictly valid only for certain frequency and distance ranges. [83] While these terms (with various adjustments) were used in scientific articles into the 1970s,[84] they are now only of historical interest. [45], The MLH scale used in some parts of Russia is actually a surface wave magnitude. The first earthquake magnitude scales were simple designations such as major/minor. [54], Despite the usefulness of the Me scale, it is not generally used due to difficulties in estimating the radiated seismic energy. The moment magnitude is denoted by Mw. Another scale of particular importance for tsunami warnings is the mantle magnitude scale, Mm. What does it mean that the earthquake occurred at a depth of 0 km? "[1], Intensity refers to the strength or force of shaking at a given location, and can be related to the peak ground velocity. Earthquake magnitude is a measure of the size of the earthquake reflecting the elastic energy released by the earthquake. How do they work? In the simplest case the moment can be calculated knowing only the amount of slip, the area of the surface ruptured or slipped, and a factor for the resistance or friction encountered. With an isoseismal map of the observed intensities (see illustration) an earthquake's magnitude can be estimated from both the maximum intensity observed (usually but not always near the epicenter), and from the extent of the area where the earthquake was felt. In order to take advantage of the growing number of globally distributed seismograph stations, new magnitude scales that are an extension of Richter's original idea were developed. [36] Lg waves attenuate quickly along any oceanic path, but propagate well through the granitic continental crust, and MbLg is often used in areas of stable continental crust; it is especially useful for detecting underground nuclear explosions.[37]. ", "Data Sheet 3.1: Magnitude calibration formulas and tables, comments on their use and complementary data. [66] For short distances (less than ~100 km) these can provide a quick estimate of magnitude before the quake's exact location is known. How do you determine the magnitude for an earthquake that occurred prior to the creation of the magnitude scale? It is referred by a certain real number on the Richter scale (such as magnitude 6.5 earthquake). [8], Most magnitude scales are based on measurements of only part of an earthquake's seismic wave-train, and therefore are incomplete. In such cases, the magnitude is considered generic and approximate. The earthquake magnitude was introduced into seismology nearly 40 yr ago, as a purely empirical concept. A variant, MLa, adapted to California and Hawaii, derives the Local magnitude (ML) from the size of the area affected by a given intensity. "Smaller" earthquakes closer to the lab or "larger" earthquakes more distant might produce the same peak amplitude, so the formula includes a distance correction for earthquakes not at the standard distance. The magnitude is a number that characterizes the relative size of an earthquake. The Moment Magnitude Scale. The various magnitude scales represent different ways of deriving magnitude from such information as is available. On top of this, seismological networks vary on how they measure seismograms. Lg waves,[35] a complex form of the Love wave which, although a surface wave, he found provided a result more closely related to the mb scale than the Ms scale. When this stress becomes great enough to rupture the crust, or to overcome the friction that prevents one block of crust from slipping past another, energy is released, some of it in the form of various kinds of seismic waves that cause ground-shaking, or quaking. Describes the scales scientists use to indicate the intensity and magnitude of an earthquake including the Mercalli, Richter, and moment magnitude. From 1935 until 1970, the earthquake magnitude scale was the Richter scale, a mathematical formula invented by Caltech seismologist Charles Richter to compare quake sizes. Seismometers, seismographs, seismograms - what's the difference? All "Local" (ML) magnitudes are based on the maximum amplitude of the ground shaking, without distinguishing the different seismic waves. Preview; Magnitudes are usually determined from measurements of an earthquake's seismic waves as recorded on a seismogram. [10], The first scale for measuring earthquake magnitudes, developed in 1935 by Charles F. Richter and popularly known as the "Richter" scale, is actually the Local magnitude scale, label ML or ML. If an amplitude of 20 millimetres as measured on a seismic signal corresponds to a magnitude 2 earthquake, then: 10 times less (2 millimetres) corresponds to a magnitude of 1; 100 times less (0.2 millimetres) corresponds to... An earthquake cannot physically occur at a depth of 0 km or -1km (above the surface of the earth). An earthquake of magnitude 4.0 or greater can cause minor or more significant damage. We've all heard earthquakes described in terms of their magnitude number. Magnitude scales describe, numerically, the size of the earthquake using mathematical equations and characteristics from the seismic waves recorded on seismographs. The idea of a logarithmic earthquake magnitude scale was first developed by Charles Richter in the 1930's for measuring the size of earthquakes occurring in southern California using relatively high-frequency data from nearby seismograph stations. The location may tell us what fault it was on and where damage (if any) most likely occurred. The Richter Scale was replaced because it worked largely for earthquakes in Southern California, and only those occurring within about 370 miles of seismometers. [50], Much of an earthquake's total energy as measured by Mw is dissipated as friction (resulting in heating of the crust). How can an earthquake have a negative depth; that would mean it’s in the air. For instance, thick layers of soft soil (such as fill) can amplify seismic waves, often at a considerable distance from the source, while sedimentary basins will often resonate, increasing the duration of shaking. The Earth's crust is stressed by tectonic forces. The circle sizes correspond to earthquake magnitude, ranging from 4.0 to 5.9 (the largest was in the Gulf of Mexico). Sensitive seismographs can record earthquakes with magnitudes of negative value and have recorded magnitudes up to about 9.0. Describes the scales scientists use to indicate the intensity and magnitude of an earthquake including the Mercalli, Richter, and moment magnitude. % Progress . Magnitude of Earthquake: Magnitude is the measure of the energy released during the earthquake. The uncertainty in an estimate of the magnitude is about plus or minus 0.3 units, and seismologists often revise magnitude estimates as they obtain and analyze additional data. HAWAI‘I ISLAND, Hawaii —The history of earthquakes and seismic monitoring in Hawai‘i during the past century will be the topic of a presentation at the University of Hawai‘i at Hilo on Thursday, January 26, at 7:00 p.m. USGS will Grant Universities $5 Million to Beef Up Public Safety Grants totaling $5 million under the American Recovery and Reinvestment Act are being awarded to 13 universities nationwide to upgrade critical earthquake monitoring networks and increase public safety. Why do we use it and where does its shape come from? What is the Modified Mercalli Intensity Scale? When this stress becomes great enough to rupture the crust, or to overcome the friction that prevents one block of crust from slipping past another, energy is released, some of it in the form of various kinds of seismic waves that cause ground-shaking, or quaking. Magnitude is determined using the logarithm of the amplitude (height) of the largest seismic wave calibrated to a scale by a seismograph. Recent developments in seismometry and earthquake source theories provide more quantitative source parameters than the magnitude. Magnitude calculations are based on a logarithmic scale, so a ten-fold drop in amplitude decreases the magnitude by 1. [19]) For several decades, earthquake magnitudes were calculated based on a method first developed by Charles Richter, a seismologist based in California. ", "Information Sheet 3.2: Proposal for unique magnitude and amplitude nomenclature", "Information Sheet 3.3: The new IASPEI standards for determining magnitudes from digital data and their relation to classical magnitudes. The Richter Scale was replaced because it worked largely for earthquakes in Southern California, and only those occurring within about 370 miles of seismometers. The regional mbLg scale – also denoted mb_Lg, mbLg, MLg (USGS), Mn, and mN – was developed by Nuttli (1973) for a problem the original ML scale could not handle: all of North America east of the Rocky Mountains. The earliest seismoscope was invented by the Chinese philosopher Chang Heng in A.D. 132. [26] Use of mB as originally defined has been largely abandoned,[27] now replaced by the standardized mBBB scale. As can be seen in the table below, this disparity of damage done is not reflected in either the moment magnitude (Mw ) nor the surface-wave magnitude (Ms ). The magnitude of an earthquake is a number that allows earthquakes to be compared with each other in terms of their relative power. magnitude. Under low-noise conditions, tsunami waves as little as 5 cm can be predicted, corresponding to an earthquake of M ~6.5.[63]. However, the length of the period influences the magnitude obtained. The size of the "felt area" can also be related to the magnitude (based on the work of Frankel 1994 and Johnston 1996). on a seismogram recorded with a Wood-Anderson torsion seismograph. In October a Mw 7.1 quake in nearly the same location, but twice as deep and on a different kind of fault, was felt over a broad area, injured over 300 people, and destroyed or seriously damaged over 10,000 houses. [13], Second, Richter arbitrarily defined the zero point of the scale to be where an earthquake at a distance of 100 km makes a maximum horizontal displacement of 0.001 millimeters (1 µm, or 0.00004 in.) In 1997 there were two large earthquakes off the coast of Chile. USGS National Seismic Hazard Maps; 2000; Article; Journal; Earthquake Spectra; Frankel, A. D.; Mueller, C. S.; Barnhard, T. P.; Leyendecker, E. V.; Wesson, R. L.; Harmsen, S. C.; Klein, F. W.; Perkins, D. M.; Dickman, N. C.; Hanson, S. L.; Hopper, M. G. Geographic Names Information System (GNIS), Mapping, Remote Sensing, and Geospatial Data, Earthquake Magnitude, Energy Release, and Shaking Intensity. [24], The original "body-wave magnitude" – mB or mB (uppercase "B") – was developed by Gutenberg (1945b, 1945c) and Gutenberg & Richter (1956) harvtxt error: no target: CITEREFGutenbergRichter1956 (help)[25] to overcome the distance and magnitude limitations of the ML scale inherent in the use of surface waves. The Earth's crust is stressed by tectonic forces. [46], Other magnitude scales are based on aspects of seismic waves that only indirectly and incompletely reflect the force of an earthquake, involve other factors, and are generally limited in some respect of magnitude, focal depth, or distance. [72] MI (upper-case letter "I", distinguished from the lower-case letter in Mi) has been used for moment magnitudes estimated from isoseismal intensities calculated per Johnston 1996. However, it is not sensitive to events smaller than about M 5.5. Where such records do not exist, magnitudes can be estimated from reports of the macroseismic events such as described by intensity scales.[68]. Earthquake magnitude and ground-shaking intensity, Japanese Meteorological Agency magnitude scale, Moment magnitude and energy magnitude scales, harvtxt error: no target: CITEREFGutenbergRichter1956 (, harvtxt error: no target: CITEREFHanksKanamori1979 (, The "USGS Earthquake Magnitude Policy" for reporting earthquake magnitudes to the public as formulated by the, harvnb error: no target: CITEREFBormannLiuRenGutdeutsch2007 (, The IASPEI standard formula for deriving moment magnitude from seismic moment is, "At Pasadena, a weighted mean is taken between, International Association of Seismology and Physics of the Earth's Interior, World-Wide Standardized Seismograph Network, https://earthquake.usgs.gov/aboutus/docs/020204mag_policy.php, "Use of the Abe magnitude scale by the Tsunami Warning System. This scale is intended for severe earthquakes. This is what was to eventually become known as the Richter magnitude. Practice. An ordinary (non-italic, non-bold) capital "M" without subscript is often used to refer to magnitude generically, where an exact value or the specific scale used is not important. Another approach is to make an isoseismal map showing the area over which a given level of intensity was felt. [33] The modern practice is to measure short-period mb scale at less than three seconds, while the broadband mBBB scale is measured at periods of up to 30 seconds.[34]. It takes into account both the energy released and the amplitude of a distant earthquake. Body-waves travel through rock directly. % Progress . Other scales have been used without a definite name, often referred to as "the method of Smith (1965)" (or similar language), with the authors often revising their method. The magnitude of the first, in July, was estimated at Mw 6.9, but was barely felt, and only in three places. Early USGS/NEIC practice was to measure mb on the first second (just the first few P-waves[32]), but since 1978 they measure the first twenty seconds. All magnitude scales retain the logarithmic scale as devised by Charles Richter, and are adjusted so the mid-range approximately correlates with the original "Richter" scale. ", "An Instrumental Earthquake Magnitude Scale", Perspective: a graphical comparison of earthquake energy release, Environmental Seismic Intensity scale (ESI), PHIVOLCS Earthquake Intensity Scale (PEIS), https://en.wikipedia.org/w/index.php?title=Seismic_magnitude_scales&oldid=1020140542, Articles using Mwp magnitude scale with duration, Creative Commons Attribution-ShareAlike License, This page was last edited on 27 April 2021, at 12:01. An earthquake has one magnitude. A modification – the "Moscow-Prague formula" – was proposed in 1962, and recommended by the IASPEI in 1967; this is the basis of the standardized Ms20 scale (Ms_20, Ms(20)). [7] Additional adjustments are made for distance, kind of crust, and the characteristics of the seismograph that recorded the seismogram. [38] For shallow earthquakes the surface waves carry most of the energy of the earthquake, and are the most destructive. "[81] Gutenberg and Richter also used an italic, non-bold "M without subscript"[82] – also used as a generic magnitude, and not to be confused with the bold, non-italic M used for moment magnitude – and a "unified magnitude" m (bolding added). Richter scale, widely used quantitative measure of an earthquake’s magnitude (size), devised in 1935 by American seismologists Charles F. Richter and Beno Gutenberg. [18] (Not to be confused with the Russian surface-wave MLH scale. [44] The MS7 scale used in China is a variant of Ms calibrated for use with the Chinese-made "type 763" long-period seismograph. This is especially useful for measuring local or regional earthquakes, both powerful earthquakes that might drive the seismometer off-scale (a problem with the analog instruments formerly used) and preventing measurement of the maximum wave amplitude, and weak earthquakes, whose maximum amplitude is not accurately measured. [74] In Japan, a network of strong-motion accelerometers provides PGA data that permits site-specific correlation with different magnitude earthquakes. Measurement of duration is incorporated in some modern scales, such as Mwpd and mBc . This magnitude scale was referred to as ML, with the L standing for local. Magnitude: Earthquake Effects: Estimated Number Each Year: 2.5 or less: Usually not felt, but … The two scales do not differ significantly for moderate size quakes (magnitudes 2 to 6) so the distinction does not matter for the general public. [14] Subsequent magnitude scales are calibrated to be approximately in accord with the original "Richter" (local) scale around magnitude 6.[15]. Based on seismic energy (K = log ES, in Joules), difficulty in implementing it using the technology of the time led to revisions in 1958 and 1960. Other Magnitude Scales There are several other scales for measuring earthquakes. Magnitude is an estimate of the relative "size" or strength of an earthquake, and thus its potential for causing ground-shaking. In order for an earthquake to occur, two blocks of crust must slip past one another, and it is impossible for this to happen at or above the surface of the earth. The moment magnitude (Mw) scale, based on the concept of seismic moment, is uniformly applicable to all sizes of earthquakes but is more difficult to compute than the other types. ", "Information Sheet 3.7: The Russian K-class system, its relationships to magnitudes and its potential for future development and application", "Chapter 3: Seismic Sources and Source Parameters", "Information Sheet 3.6: Radiated seismic energy and energy magnitude", "The Radiated Seismic Energy and Apparent Stress of Interplate and Intraslab Earthquakes at Subduction Zone Environments: Implications for Seismic Hazard Estimation", "Operational Procedures of Contributing Agencies", "Amplitudes of surface Waves and magnitudes of shallow earthquakes", "Magnitude determination for deep-focus earthquakes", "Earthquake Monitoring in Southern California for Seventy-Seven Years (1932—2008)", "The energy release in great earthquakes", "Magnitude Scale and Quantification of Earthquake", "Chapter 12: Intensity and Intensity Scales", "Origins and Methodology of the Russian Energy K-Class System and Its Relationship to Magnitude Scales", "Developing Composite Regional Catalogs of the Seismicity of the Former Soviet Union. 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