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Earthquake

Global earthquake epicenters, 1963–1998

An earthquake is a sudden and sometimes catastrophic movement of a part of the Earth's surface. Earthquakes result from the dynamic release of elastic strain energy that radiates seismic waves. Earthquakes typically result from the movement of faults, planar zones of deformation within the Earth's upper crust. The word earthquake is also widely used to indicate the source region itself. The Earth's lithosphere is a patch work of plates in slow but constant motion (see plate tectonics). Earthquakes occur where the stress resulting from the differential motion of these plates exceeds the strength of the crust. The highest stress (and possible weakest zones) are most often found at the boundaries of the tectonic plates and hence these locations are where the majority of earthquakes occur. Events located at plate boundaries are called interplate earthquakes; the less frequent events that occur in the interior of the lithospheric plates are called intraplate earthquakes (see, for example, New Madrid Seismic Zone). Earthquakes related to plate tectonics are called tectonic earthquakes. Most earthquakes are tectonic, but they also occur in volcanic regions and as the result of a number of anthropogenic sources, such as reservoir induced seismicity, mining and the removal or injection of fluids into the crust. Seismic waves including some strong enough to be felt by humans can also be caused by explosions (chemical or nuclear), landslides, and collapse of old mine shafts, though these sources are not strictly earthquakes.

Characteristics

Large numbers of earthquakes occur on a daily basis on Earth, but the majority of them are detected only by seismometers and cause no damage .

Most earthquakes occur in narrow regions around plate boundaries down to depths of a few tens of kilometres where the crust is rigid enough to support the elastic strain. Where the crust is thicker and colder they will occur at greater depths and the opposite in areas that are hot. At subduction zones where plates descend into the mantle, earthquakes have been recorded to a depth of 600 km, although these deep earthquakes are caused by different mechanisms than the more common shallow events. Some deep earthquakes may be due to the transition of olivine to spinel, which is more stable in the deep mantle.

Large earthquakes can cause serious destruction and massive loss of life through a variety of agents of damage, including fault rupture, vibratory ground motion (i.e., shaking), inundation (e.g., tsunami, seiche, dam failure), various kinds of permanent ground failure (e.g. liquefaction, landslide), and fire or a release of hazardous materials. In a particular earthquake, any of these agents of damage can dominate, and historically each has caused major damage and great loss of life, but for most of the earthquakes shaking is the dominant and most widespread cause of damage. There are four types of seismic waves that are all generated simultaneously and can be felt on the ground. S-waves (secondary or shear waves) and the two types of surfaces waves (Love waves and Rayleigh waves) are responsible for the shaking hazard.

Damage from the 1906 San Francisco earthquake. Section of collapsed freeway after the 1989 Loma Prieta earthquake.

Most large earthquakes are accompanied by other, smaller ones, that can occur either before or after the principal quake — these are known as foreshocks or aftershocks, respectively. While almost all earthquakes have aftershocks, foreshocks are far less common occurring in only about 10% of events. The power of an earthquake is distributed over a significant area, but in the case of large earthquakes, it can spread over the entire planet. Ground motions caused by very distant earthquakes are called teleseisms. The Rayleigh waves from the Sumatra-Andaman Earthquake of 2004 caused ground motion of over 1 cm even at the seismometers that were located far from it, although this displacement was abnormally large. Using such ground motion records from around the world it is possible to identify a point from which the earthquake's seismic waves appear to originate. That point is called its "focus" or "hypocenter" and usually proves to be the point at which the fault slip was initiated. The location on the surface directly above the hypocenter is known as the "epicenter". The total size of the fault that slips, the rupture zone, can be as large as 1000 km, for the biggest earthquakes. Just as a large loudspeaker can produce a greater volume of sound than a smaller one, large faults are capable of higher magnitude earthquakes than smaller faults are.

Earthquakes that occur below sea level and have large vertical displacements can give rise to tsunamis, either as a direct result of the deformation of the sea bed due to the earthquake or as a result of submarine landslips or "slides" directly or indirectly triggered by it.

Earthquake Size

The first method of quantifying earthquakes was intensity scales. In the United States the Mercalli (or Modified Mercalli, MM) scale is commonly used, while Japan (shindo) and the EU (European Macroseismic Scale) each have their own scales. These assign a numeric value (different for each scale) to a location based on the size of the shaking experienced there. The value 6 (normally denoted "VI") in the MM scale for example is:

Everyone feels movement. People have trouble walking. Objects fall from shelves. Pictures fall off walls. Furniture moves. Plaster in walls might crack. Trees and bushes shake. Damage is slight in poorly built buildings. No structural damage.

A Shakemap recorded by the Pacific Northwest Seismograph Network that shows the instrument recorded intensity of the shaking of the Nisqually earthquake on February 28, 2001. A Community Internet Intensity Map generated by the USGS that shows the intensity felt by humans by ZIP Code of the shaking of the Nisqually earthquake on February 28, 2001.

The problem with these scales is the measurement is subjective, often based on the worst damage in an area and influenced by local effects like site conditions that make it a poor measure for the relative size of different events in different places. For some tasks related to engineering and local planning it is still useful for the very same reasons and thus still collected. If you feel an earthquake in the US you can report the effects to the USGS.

The first attempt to qualitatively define one value to describe the size of earthquakes was the magnitude scale (the name being taking from similar formed scales used on the brightness of stars). In the 1930s, a California seismologist named Charles F. Richter devised a simple numerical scale (which he called the magnitude) to describe the relative sizes of earthquakes in Southern California. This is known as the “Richter scale”, “Richter Magnitude” or “Local Magnitude” (ML). It 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 600km from the earthquake. Other more recent Magnitude measurements include: body wave magnitude (mb), surface wave magnitude (Ms) and duration magnitude (MD). Each of these is scaled to gives values similar to the values given by the Richter scale. However as each is also based on the measurement of one part of the seismogram they do not measure the overall power of the source and can suffer from saturation at higher magnitude values (larger events fail to produce higher magnitude values).These scales are also empirical and as such there is no physical meaning to the values. They are still useful however as they can be rapidly calculated, there are catalogues of them dating back many years and are they are familiar to the public. Seismologists now favor a measure called the seismic moment, related to the concept of moment in physics, to measure the size of a seismic source. The seismic moment is calculated from seismograms but can also by obtained from geologic estimates of the size of the fault rupture and the displacement. The values of moments for different earthquakes ranges over several order of magnitude. As a result the moment magnitude (MW) scale was introduced by Hiroo Kanamori, which is comparable to the other magnitude scales but will not saturate at higher values.

Larger earthquakes occur less frequently than smaller earthquakes, the relationship being exponential, ie roughly ten times as many earthquakes larger than 4 occur in a particular time period than earthquakes larger than magnitude 5. For example it has been calculated that the average recurrence for the United Kingdom can be described as follows:

  • an earthquake of 3.7 or larger every 1 year
  • an earthquake of 4.7 or larger every 10 years
  • an earthquake of 5.6 or larger every 100 years.

Causes

Most earthquakes are powered by the release of the elastic strain that accumulate over time, typically, at the boundaries of the plates that make up the Earth's lithosphere via a process called Elastic-rebound theory. The Earth is made up of tectonic plates driven by the heat in the Earth's mantle and core. Where these plates meet stress accumulates. Eventually when enough stress accumulates, the plates move, causing an earthquake. Deep focus earthquakes, at depths of 100's km, are possibly generated as subducted lithospheric material catastrophically undergoes a phase transition since at the pressures and temperatures present at such depth elastic strain cannot be supported. Some earthquakes are also caused by the movement of magma in volcanoes, and such quakes can be an early warning of volcanic eruptions. A rare few earthquakes have been associated with the build-up of large masses of water behind dams, such as the Kariba Dam in Zambia, Africa, and with the injection or extraction of fluids into the Earth's crust (e.g. at certain geothermal power plants and at the Rocky Mountain Arsenal). Such earthquakes occur because the strength of the Earth's crust can be modified by fluid pressure. Earthquakes have also been known to be caused by the removal of natural gas from subsurface deposits, for instance in the northern Netherlands. Finally, ground shaking can also result from the detonation of explosives. Thus scientists have been able to monitor, using the tools of seismology, nuclear weapons tests performed by governments that were not disclosing information about these tests along normal channels. Earthquakes such as these, that are caused by human activity, are referred to by the term induced seismicity.

Another type of movement of the Earth is observed by terrestrial spectroscopy. These oscillations of the earth are either due to the deformation of the Earth by tide caused by the Moon or the Sun, or other phenomena.

A recently proposed theory suggests that some earthquakes may occur in a sort of earthquake storm, where one earthquake will trigger a series of earthquakes each triggered by the previous shifts on the fault lines, similar to aftershocks, but occurring years later.

Preparation for earthquakes

  • Emergency preparedness
  • Household seismic safety
  • Seismic retrofit
  • Earthquake prediction

Specific fault articles

  • Alpine Fault
  • Calaveras Fault
  • Hayward Fault Zone
  • North Anatolian Fault Zone
  • New Madrid Fault Zone
  • San Andreas Fault

Specific earthquake articles

  • Shaanxi Earthquake (1556). Deadliest known earthquake in history, estimated to have killed 830,000 in China.
  • Cascadia Earthquake (1700).
  • Kamchatka earthquakes (1737 and 1952).
  • Lisbon earthquake (1755).
  • New Madrid Earthquake (1811).
  • Fort Tejon Earthquake (1857).
  • Charleston earthquake (1886). Largest earthquake in the Southeast and killed 100.
  • San Francisco Earthquake (1906).
  • Great Kanto earthquake (1923). On the Japanese island of Honshu, killing over 140,000 in Tokyo and environs.
  • Kamchatka earthquakes (1952 and 1737).
  • Great Chilean Earthquake (1960). Biggest earthquake ever recorded, 9.5 on Moment magnitude scale.
  • Good Friday Earthquake (1964) Alaskan earthquake.
  • Ancash earthquake (1970). Caused a landslide that buried the town of Yungay, Peru; killed over 40,000 people.
  • Sylmar earthquake (1971). Caused great and unexpected destruction of freeway bridges and flyways in the San Fernando Valley, leading to the first major seismic retrofits of these types of structures, but not at a sufficient pace to avoid the next California freeway collapse in 1989.
  • Tangshan earthquake (1976). The most destructive earthquake of modern times. The official death toll was 255,000, but many experts believe that two or three times that number died.
  • Great Mexican Earthquake (1985). 8.1 on the Richter Scale, killed over 6,500 people (though it is believed as many as 30,000 may have died, due to missing people never reappearing.)
  • Whittier Narrows earthquake (1987).
  • Armenian earthquake (1988). Killed over 25,000.
  • Loma Prieta earthquake (1989). Severely affecting Santa Cruz, San Francisco and Oakland in California. Revealed necessity of accelerated seismic retrofit of road and bridge structures.
  • Northridge, California earthquake (1994). Damage showed seismic resistance deficiencies in modern low-rise apartment construction.
  • Great Hanshin earthquake (1995). Killed over 6,400 people in and around Kobe, Japan.
  • İzmit earthquake (1999) Killed over 17,000 in northwestern Turkey.
  • Düzce earthquake (1999)
  • Chi-Chi earthquake (1999).
  • Nisqually Earthquake (2001).
  • Gujarat Earthquake (2001).
  • Dudley Earthquake (2002).
  • Bam Earthquake (2003).
  • Parkfield, California earthquake (2004). Not large (6.0), but the most anticipated and intensely instrumented earthquake ever recorded and likely to offer insights into predicting future earthquakes elsewhere on similar slip-strike fault structures.
  • Chuetsu Earthquake (2004).
  • Indian Ocean Earthquake (2004). One of the largest earthquakes ever recorded at 9.0. Epicenter off the coast of the Indonesian island Sumatra. Triggered a tsunami which caused nearly 300,000 deaths spanning several countries.
  • Sumatran Earthquake (2005).
  • Fukuoka earthquake (2005).
  • Kashmir earthquake (2005). Killed over 79,000 people. Many more at risk from the Kashmiri winter.
  • Lake Tanganyika earthquake (2005).

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A recently proposed theory suggests that some earthquakes may occur in a sort of earthquake storm, where one earthquake will trigger a series of earthquakes each triggered by the previous shifts on the fault lines, similar to aftershocks, but occurring years later. Conversely, other sects consider Venus to be some form of paradise or an advanced secret base for angels/aliens to operate from. These oscillations of the earth are either due to the deformation of the Earth by tide caused by the Moon or the Sun, or other phenomena. Its extremely high surface temperature and impenetrable cloud cover cause people to believe that the fires of Hell burn on the surface, obscured from our earthly view. Another type of movement of the Earth is observed by terrestrial spectroscopy. There are some religious sects who believe that Hell may be located on Venus. Earthquakes such as these, that are caused by human activity, are referred to by the term induced seismicity. Until it was penetrated by probes, Venus's opaque cloud layer gave science fiction writers free rein in imagining the planet's surface, and they frequently imagined it to be Earthlike.

Thus scientists have been able to monitor, using the tools of seismology, nuclear weapons tests performed by governments that were not disclosing information about these tests along normal channels. The association with sex and femininity is supposed to relate to the period of 266 days between the conjunction and maximum elongation of Venus, which corresponds more or less to the length of human pregnancy. Finally, ground shaking can also result from the detonation of explosives. Alchemists constructed the symbol from a circle (representing spirit) above a cross (representing matter). Earthquakes have also been known to be caused by the removal of natural gas from subsurface deposits, for instance in the northern Netherlands. The Venus symbol also represents femininity, and in ancient alchemy stood for copper. Such earthquakes occur because the strength of the Earth's crust can be modified by fluid pressure. Its symbol is the sign also used in biology for the female sex, a stylized representation of the goddess Venus's hand mirror: a circle with a small cross underneath (Unicode: ♀).

at certain geothermal power plants and at the Rocky Mountain Arsenal). To the Jews it is known as Noga ("shining"), Ayeleth-ha-Shakhar ("deer of the dawn") and Kochav-ha-'Erev ("star of the evening"). A rare few earthquakes have been associated with the build-up of large masses of water behind dams, such as the Kariba Dam in Zambia, Africa, and with the injection or extraction of fluids into the Earth's crust (e.g. The Maasai people in Africa named the planet Kileken, and have a myth about it called "The Orphan Boy." The Morning Star was called the Bearer of Light ("phōsphoros" or "eōsphoros" in Greek and "Lucifer" in Latin, a term later used of the fallen angel cast out of heaven, see Isaiah 14:12). Some earthquakes are also caused by the movement of magma in volcanoes, and such quakes can be an early warning of volcanic eruptions. Venus was known to ancient Babylonians around 1600 BC, and to the Mayan civilization (the Mayans developed a religious calendar based on Venus's motion) and must have been known long before in prehistoric times, given that it is the third brightest object in the sky after the Sun and Moon. Deep focus earthquakes, at depths of 100's km, are possibly generated as subducted lithospheric material catastrophically undergoes a phase transition since at the pressures and temperatures present at such depth elastic strain cannot be supported. When viewed from Earth, the successive conjunctions of Venus plot the points of a pentagram around the Sun in an eight-year cycle (see Orbit).

Eventually when enough stress accumulates, the plates move, causing an earthquake. It is most likely to have originated from the observations of prehistoric astronomers. Where these plates meet stress accumulates. The pentagram has long been associated with the planet Venus and the worship of the goddess Venus, or her equivalent. The Earth is made up of tectonic plates driven by the heat in the Earth's mantle and core. Some speculate that the mysterious dark streaks seen in the atmosphere through ultraviolet filters could be colonies of microbes absorbing sunlight for their metabolism. Most earthquakes are powered by the release of the elastic strain that accumulate over time, typically, at the boundaries of the plates that make up the Earth's lithosphere via a process called Elastic-rebound theory. Recent spectrographic observations have found carbonyl sulfide in the atmosphere of Venus, a chemical that is very difficult to make via natural processes and usually associated with life.

For example it has been calculated that the average recurrence for the United Kingdom can be described as follows:. Some speculate that spores from Earth could hitch a ride on small passing asteroids and survive a trip to Venus's atmosphere. Larger earthquakes occur less frequently than smaller earthquakes, the relationship being exponential, ie roughly ten times as many earthquakes larger than 4 occur in a particular time period than earthquakes larger than magnitude 5. However, the cloud cover supports fairly life-friendly conditions at higher altitudes. As a result the moment magnitude (MW) scale was introduced by Hiroo Kanamori, which is comparable to the other magnitude scales but will not saturate at higher values. Space probes in the 1960's made it pretty clear that the surface of Venus is far too hot to support life as we know it. The values of moments for different earthquakes ranges over several order of magnitude. For elongations and other aspects, see Aspects of Venus.

The seismic moment is calculated from seismograms but can also by obtained from geologic estimates of the size of the fault rupture and the displacement. Venus sky movement patterns have been observed several times within the past 4000 years by a number of people, including the Greeks. Seismologists now favor a measure called the seismic moment, related to the concept of moment in physics, to measure the size of a seismic source. Venus is now known to be moonless. They are still useful however as they can be rapidly calculated, there are catalogues of them dating back many years and are they are familiar to the public. These sightings have since been discredited, and are thought to have been either spurious internal reflections, mostly faint stars that happened to be in the right place at the right time, or maybe even asteroids passing by the planet. However as each is also based on the measurement of one part of the seismogram they do not measure the overall power of the source and can suffer from saturation at higher magnitude values (larger events fail to produce higher magnitude values).These scales are also empirical and as such there is no physical meaning to the values. German astronomers called the moon Kleinchen (literally "tiny"), and sporadic sightings by astronomers continued until 1892.

Each of these is scaled to gives values similar to the values given by the Richter scale. Venus was once thought to possess a moon, named Neith after the chief goddess of Sais, Egypt (whose veil no mortal raised), first observed by Giovanni Domenico Cassini in 1672. Other more recent Magnitude measurements include: body wave magnitude (mb), surface wave magnitude (Ms) and duration magnitude (MD). There are about 30 arachnoids on Venus. It 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 600km from the earthquake. They are quite different from the volcanoes on earth, and are formed differently too. This is known as the “Richter scale”, “Richter Magnitude” or “Local Magnitude” (ML). There are also other bodies that spout lava, known as arachnoids, for their spiderweb-like look.

Richter devised a simple numerical scale (which he called the magnitude) to describe the relative sizes of earthquakes in Southern California. Venus has many active volcanoes similar to those on Earth, so there is a lot of lava present on the surface. In the 1930s, a California seismologist named Charles F. Because of dryness, Venus's rocks are much harder than Earth's, which leads to steeper mountains, cliffs and other features. The first attempt to qualitatively define one value to describe the size of earthquakes was the magnitude scale (the name being taking from similar formed scales used on the brightness of stars). Molecular oxygen is thought to have combined with atoms in the crust (large amounts of oxygen, however, remain in the atmosphere in the form of carbon dioxide). If you feel an earthquake in the US you can report the effects to the USGS. Therefore, the hydrogen escaped into space because of its low molecular mass; the ratio of hydrogen to deuterium (a heavier isotope of hydrogen which doesn't escape as quickly) in Venus's atmosphere seems to support this theory.

For some tasks related to engineering and local planning it is still useful for the very same reasons and thus still collected. It is thought that Venus originally had as much water as Earth, but that water vapor in the upper atmosphere was split into hydrogen and oxygen due to solar wind. The problem with these scales is the measurement is subjective, often based on the worst damage in an area and influenced by local effects like site conditions that make it a poor measure for the relative size of different events in different places. As a result, solar wind strikes Venus's upper atmosphere without mediation. No structural damage. This may be due to its slow rotation being insufficient to drive an internal dynamo of liquid iron. Damage is slight in poorly built buildings. Venus's intrinsic magnetic field has been found very weak compared to other planets in the solar system.

Trees and bushes shake. Other recent findings suggest that Venus is still volcanically active in isolated geological hotspots. Plaster in walls might crack. It is theorized that Venus does not have mobile plate tectonics as Earth does, but instead undergoes massive volcanic upwellings at regular intervals that inundate its surface with fresh lava. Furniture moves. Recent results from the Magellan gravity data indicate that Venus's crust is stronger and thicker than had previously been assumed. Pictures fall off walls. The interior of Venus is probably similar to that of Earth: an iron core about 3000 km in radius, with a molten rocky mantle making up the majority of the planet.

Objects fall from shelves. This suggests that Venus underwent a major resurfacing event in the not too distant geological past. People have trouble walking. The oldest features present on Venus seem to be only around 800 million years old, with most of the terrain being considerably younger (though still not less than several hundred million years for the most part). Everyone feels movement. Nearly 90% of Venus's surface appears to consist of recently (in the geological sense) solidified basaltic lava, with very few meteorite craters. The value 6 (normally denoted "VI") in the MM scale for example is:. Because of this, no impact crater smaller than about 3 km (2 mi) in diameter can form.

These assign a numeric value (different for each scale) to a location based on the size of the shaking experienced there. Venus' thick atmosphere causes meteors to decelerate as they fall toward the surface, and even large meteors will strike the surface at too low a speed to form an impact crater if they have less than a certain threshold kinetic energy. In the United States the Mercalli (or Modified Mercalli, MM) scale is commonly used, while Japan (shindo) and the EU (European Macroseismic Scale) each have their own scales. With only the exception of Maxwell Montes, all surface features on Venus are named after real or mythological females. The first method of quantifying earthquakes was intensity scales. Between these highlands are a number of broad depressions, including Atalanta Planitia, Guinevere Planitia, and Lavinia Planitia. Earthquakes that occur below sea level and have large vertical displacements can give rise to tsunamis, either as a direct result of the deformation of the sea bed due to the earthquake or as a result of submarine landslips or "slides" directly or indirectly triggered by it. In the southern hemisphere is the larger Aphrodite Terra, about the size of South America.

Just as a large loudspeaker can produce a greater volume of sound than a smaller one, large faults are capable of higher magnitude earthquakes than smaller faults are. Ishtar Terra is about the size of Australia. The total size of the fault that slips, the rupture zone, can be as large as 1000 km, for the biggest earthquakes. The northern highland is named Ishtar Terra and has Venus's highest mountains, named the Maxwell Montes (roughly 2 km taller than Mount Everest) after James Clerk Maxwell, which surround the plateau Lakshmi Planum. The location on the surface directly above the hypocenter is known as the "epicenter". Venus has two major continent-like highlands on its surface, rising over vast plains. That point is called its "focus" or "hypocenter" and usually proves to be the point at which the fault slip was initiated. 16.

Using such ground motion records from around the world it is possible to identify a point from which the earthquake's seismic waves appear to originate. 28, 2002, p. The Rayleigh waves from the Sumatra-Andaman Earthquake of 2004 caused ground motion of over 1 cm even at the seismometers that were located far from it, although this displacement was abnormally large. New Scientist, Sept. Ground motions caused by very distant earthquakes are called teleseisms. Some have suggested that microbes exist in the clouds (which also contain droplets of water), and produce these components from water, carbon monoxide and sulfur dioxide. The power of an earthquake is distributed over a significant area, but in the case of large earthquakes, it can spread over the entire planet. It is unclear how the carbonyl sulfide could be formed--it is often a sign of biological activity.

While almost all earthquakes have aftershocks, foreshocks are far less common occurring in only about 10% of events. Hydrogen sulfide reacts with sulfur dioxide, which implies that some process must be creating these components. Most large earthquakes are accompanied by other, smaller ones, that can occur either before or after the principal quake — these are known as foreshocks or aftershocks, respectively. The atmosphere also contains hydrogen sulfide (H2S) and carbonyl sulfide (COS). S-waves (secondary or shear waves) and the two types of surfaces waves (Love waves and Rayleigh waves) are responsible for the shaking hazard. (This makes the surface temperature hot enough to melt lead.). There are four types of seismic waves that are all generated simultaneously and can be felt on the ground. The minimal value of the temperature, listed in the table, refers to cloud tops —the surface temperature is never below 400 °C (750 °F).

In a particular earthquake, any of these agents of damage can dominate, and historically each has caused major damage and great loss of life, but for most of the earthquakes shaking is the dominant and most widespread cause of damage. The mean surface temperature of Venus, as given by NASA, is 464 °C (864 °F). liquefaction, landslide), and fire or a release of hazardous materials. The temperature at the tops of these clouds is approximately −45 °C (−50 °F). Large earthquakes can cause serious destruction and massive loss of life through a variety of agents of damage, including fault rupture, vibratory ground motion (i.e., shaking), inundation (e.g., tsunami, seiche, dam failure), various kinds of permanent ground failure (e.g. The clouds are mainly composed of sulfur dioxide and sulfuric acid droplets and cover the planet completely, obscuring any surface details from the human eye. Some deep earthquakes may be due to the transition of olivine to spinel, which is more stable in the deep mantle. However, owing to the high density of the atmosphere at Venus's surface, even such slow winds exert a significant amount of force against obstructions.

At subduction zones where plates descend into the mantle, earthquakes have been recorded to a depth of 600 km, although these deep earthquakes are caused by different mechanisms than the more common shallow events. There are strong 300 km/h (200 mph) winds at the cloud tops, but winds at the surface are very slow, no more than a few miles per hour. Where the crust is thicker and colder they will occur at greater depths and the opposite in areas that are hot. The immense quantity of CO2 in the atmosphere is what traps the heat by the greenhouse mechanism. Most earthquakes occur in narrow regions around plate boundaries down to depths of a few tens of kilometres where the crust is rigid enough to support the elastic strain. The cloud cover keeps the planet much cooler than it would be otherwise. Large numbers of earthquakes occur on a daily basis on Earth, but the majority of them are detected only by seismometers and cause no damage . A common conceptual misunderstanding regarding Venus is the mistaken belief that its thick cloud cover traps heat, as the opposite is actually true.

. In the absence of any greenhouse effect, the temperature at the surface of Venus would be quite similar to Earth. Seismic waves including some strong enough to be felt by humans can also be caused by explosions (chemical or nuclear), landslides, and collapse of old mine shafts, though these sources are not strictly earthquakes. Thus, despite being closer to the Sun than Earth, the surface of Venus is not as well heated and even less well lit by the Sun. Most earthquakes are tectonic, but they also occur in volcanic regions and as the result of a number of anthropogenic sources, such as reservoir induced seismicity, mining and the removal or injection of fluids into the crust. Venus's bolometric albedo is approximately 60%, and its visual light albedo is even greater. Earthquakes related to plate tectonics are called tectonic earthquakes. This prevents most of the sunlight from ever heating the surface.

Events located at plate boundaries are called interplate earthquakes; the less frequent events that occur in the interior of the lithospheric plates are called intraplate earthquakes (see, for example, New Madrid Seismic Zone). The solar irradiance is so much lower at the surface of Venus because the planet's thick cloud cover reflects the majority of the sunlight back into space. The highest stress (and possible weakest zones) are most often found at the boundaries of the tectonic plates and hence these locations are where the majority of earthquakes occur. Upper atmosphere winds circling the planet approximately every 4 days help distribute the heat to other areas on the surface. Earthquakes occur where the stress resulting from the differential motion of these plates exceeds the strength of the crust. Owing to the thermal inertia and convection of its dense atmosphere, the temperature does not vary significantly between the night and day sides of Venus despite its extremely slow rotation of less than one rotation per Venusian year, meaning that, at the equator, Venus' surface rotates at a mere 6.5 km/h (4 mph). The Earth's lithosphere is a patch work of plates in slow but constant motion (see plate tectonics). This makes Venus's surface hotter than Mercury's, even though Venus is nearly twice as distant from the Sun and only receives 25% of the solar irradiance (2613.9 W/m² in the upper atmosphere, and just 1071.1 W/m² at the surface).

The word earthquake is also widely used to indicate the source region itself. This enormously CO2-rich atmosphere results in a strong greenhouse effect that raises the surface temperature more than 400 °C (750 °F) above what it would be otherwise, causing temperatures at the surface to reach extremes as great as 500 °C (930 °F) in low elevation regions near the planet's equator. Earthquakes typically result from the movement of faults, planar zones of deformation within the Earth's upper crust. Venus has an atmosphere consisting mainly of carbon dioxide and a small amount of nitrogen, with a pressure at the surface about 90 times that of Earth (a pressure equivalent to a depth of 1 kilometer under Earth's oceans); its atmosphere is also roughly 90 times more massive than ours. Earthquakes result from the dynamic release of elastic strain energy that radiates seismic waves. This may simply be a coincidence, but there is some speculation that this may be the result of tidal locking, with tidal forces affecting Venus' rotation whenever the planets get close enough together —although the tides raised by Venus on Earth are vanishingly small. An earthquake is a sudden and sometimes catastrophic movement of a part of the Earth's surface. In addition to this unusual retrograde rotation, the periods of Venus' rotation and of its orbit are synchronized in such a way that it always presents the same face toward Earth when the two planets are at their closest approach (5.001 Venusian solar days between each inferior conjunction).

Lake Tanganyika earthquake (2005). [1] If the Sun could be seen from Venus' surface, it would appear to rise in the west and set in the east for a 116.75 day-night cycle (Venus' mean solar day), and a Venusian year would thus last 1.92 Venusian "days". Many more at risk from the Kashmiri winter. (Pluto and Uranus also have retrograde rotation, though Uranus's axis, tilted at 97.86 degrees, almost lies in its orbital plane.) A slow retrograde rotation is thought to have developed as a consequence of tidal forces, friction, and solar heating of Venus' thick atmosphere. Killed over 79,000 people. Venus has a slow retrograde rotation, meaning it rotates from east to west, instead of west to east as most of the other major planets do. Kashmir earthquake (2005). This will be the closest approach of Venus to earth until December 16th, 2101 when Venus will reach a distance of 0.26431736 AU = 39,541,578 kilometres to earth.

Fukuoka earthquake (2005). On December 16th, 1850, Venus reached the lowest distance to earth since 1800, with a value of 0.26413854 AU = 39,514,827 kilometres. Sumatran Earthquake (2005). At inferior conjunction, Venus can get closer to earth than any other planet--little more than 100 times the Moon's average distance. Triggered a tsunami which caused nearly 300,000 deaths spanning several countries. Another association is with the Moon, because 2920 days equal almost exactly 99 lunations (29.5 * 99 = 2920.5). Epicenter off the coast of the Indonesian island Sumatra. This was known as the Sothis cycle in ancient Egypt, and was familiar to the Maya as well.

One of the largest earthquakes ever recorded at 9.0. Since 5 * 584 = 2920, which is equivalent to 8 * 365 Venus returns to the same point in the sky every 8 years (minus two leap days). Indian Ocean Earthquake (2004). After these 584 days Venus is visible in a position 72 degrees away from the previous one. Chuetsu Earthquake (2004). The cycle between one maximum elongation and the next lasts 584 days. Not large (6.0), but the most anticipated and intensely instrumented earthquake ever recorded and likely to offer insights into predicting future earthquakes elsewhere on similar slip-strike fault structures. It is sometimes referred to as the "Morning Star" or the "Evening Star", and when it is visible in dark skies it is by far the brightest star-like object in the sky.

Parkfield, California earthquake (2004). However, when at its brightest, Venus may be seen during the daytime, making it the only heavenly body that can be seen both day and night besides the Moon. Bam Earthquake (2003). As Venus is closer to the Sun than the Earth, it always appears in roughly the same direction from Earth as the Sun (the greatest elongation is 47.8°), so on Earth it can usually only be seen a few hours before sunrise or a few hours after sunset. Dudley Earthquake (2002). Although all planets' orbits are elliptical, Venus's orbit is the closest to circular, with an eccentricity of less than 1%. Gujarat Earthquake (2001). The Chinese, Korean, Japanese and Vietnamese cultures refer to the planet as the metal star, 金星, based on the Five Elements.

Nisqually Earthquake (2001). Other less common adjectives include Venerean, Venerian, and Veneran. Chi-Chi earthquake (1999). Some astronomers use Cytherean, which comes from Cytherea, another name for Aphrodite in ancient Greek Mythology. Düzce earthquake (1999). The adjective Venusian is commonly used for Venus, but the Latin adjective is Venereal, which is avoided because of its modern association with sexually transmitted diseases. İzmit earthquake (1999) Killed over 17,000 in northwestern Turkey. Venus is named after the Roman goddess of love, Venus.

Killed over 6,400 people in and around Kobe, Japan. . Great Hanshin earthquake (1995). The planet Venus is also termed Lucifer when appearing as the morning star. Damage showed seismic resistance deficiencies in modern low-rise apartment construction. A terrestrial planet, it is sometimes called Earth's "sister planet", as the two are very similar in size and bulk composition. Northridge, California earthquake (1994). Venus is the second planet from the Sun.

Revealed necessity of accelerated seismic retrofit of road and bridge structures. The terraforming of Venus provides the setting of Pamela Sargent's Venus series, Venus of Dreams, Venus of Shadows, and Children of Venus.. Severely affecting Santa Cruz, San Francisco and Oakland in California. A more scientifically accurate depiction of the planet is offered in Ben Bova's novel Venus (2000, ISBN 031287216X)-. Loma Prieta earthquake (1989). Also, on her forehead is the planet's symbol. Killed over 25,000. Her image colours are gold and orange--similar to the colour of the planet.

Armenian earthquake (1988). Venus Love Me Chain and Venus Love and Beauty Shock) represent the idea of love and femininity. Whittier Narrows earthquake (1987). In mythology, Venus is the Roman goddess of love (Aphrodite in Greek), therefore, Sailor Venus's attacks and weapons (e.g. 8.1 on the Richter Scale, killed over 6,500 people (though it is believed as many as 30,000 may have died, due to missing people never reappearing.). In the Japanese anime series, Bishoujo Senshi Sailor Moon (1992), Sailor Venus is a soldier representing the planet of the same name. Great Mexican Earthquake (1985). In the cartoon Exosquad, terraformed Venus was portrayed as one of the three habitable planets in the solar system (the others being Earth and Mars).

The official death toll was 255,000, but many experts believe that two or three times that number died. Much of the population lived in floating cities in the sky. The most destructive earthquake of modern times. In the show, Venus was revealed to be an arid but habitable world. Tangshan earthquake (1976). A presumably terraformed Venus was the setting of one episode of the anime Cowboy Bebop (1998). Caused great and unexpected destruction of freeway bridges and flyways in the San Fernando Valley, leading to the first major seismic retrofits of these types of structures, but not at a sufficient pace to avoid the next California freeway collapse in 1989. Clarke's 3001: The Final Odyssey (1997).

Sylmar earthquake (1971). Venus is briefly mentioned in Arthur C. Caused a landslide that buried the town of Yungay, Peru; killed over 40,000 people. In Jacqueline Susann's Yargo (1979), Venus is inhabited by bees that are as big as horses. Ancash earthquake (1970). Venus is the location of several Starfleet Academy training facilities and terraforming stations in the fictional Star Trek universe (1966–). Good Friday Earthquake (1964) Alaskan earthquake. The novel The Land of Crimson Clouds (Strana Bagrovykh Tuch in the original) describes the first successful manned mission to Venus, although a full-scaled colonization of the planet was not initiated until much later (in 2119; see Noon: 22nd Century).

Biggest earthquake ever recorded, 9.5 on Moment magnitude scale. In the Noon Universe created by the Soviet science fiction writers Boris and Arkady Strugatsky, Venus is depicted as an extremely harsh planet covered by strange flora and fauna but also very rich in minerals and heavy metals. Great Chilean Earthquake (1960). Many science-fiction movies and serials of the '50s and '60s, such as Abbott and Costello Go to Mars, Space Ship Sappy and Space Patrol, have used Venus' namesake goddess and her domain to contrive planetary populations of nubile women welcoming (or attacking) all-male astronaut crews. Kamchatka earthquakes (1952 and 1737). Venus was the home planet of the Mekon, arch-enemy of the 1950s comic book hero Dan Dare. On the Japanese island of Honshu, killing over 140,000 in Tokyo and environs. Moore, underwater city-states hire mercenary companies and their battleships to fight their wars on the surface.

Great Kanto earthquake (1923). L. San Francisco Earthquake (1906). In the military science fiction classic Clash by Night (1943) by Henry Kuttner (writing as Lawrence O'Donnell) and C. Largest earthquake in the Southeast and killed 100. Lewis, Perelandra (1943) takes place on Venus (called by the natives Perelandra), the site of a second garden of Eden. Charleston earthquake (1886). The second book of the Space Trilogy (1938–1945) by C.S.

Fort Tejon Earthquake (1857). Lovecraft and Kenneth Sterling short story 'In the Walls of Eryx' (1939), takes place on Venus, but is not considered part of the Cthulhu Mythos. New Madrid Earthquake (1811). P. Lisbon earthquake (1755). The H. Kamchatka earthquakes (1737 and 1952). [2].

Cascadia Earthquake (1700). Edgar Rice Burroughs wrote a series of five books on Venus (the Venus series), featuring hero Carson Napier, who discovers that Venus (or Amtor, as it is known by the Venusians) is a world of sky-high trees, warring kingdoms and princesses in need of rescue. Deadliest known earthquake in history, estimated to have killed 830,000 in China. Lovecraft's Cthulhu Mythos (1928–), there are mentions of the 'Lords of Venus', and conflicting indications that the Serpent People originated there. Shaanxi Earthquake (1556). P. San Andreas Fault. In H.

New Madrid Fault Zone. In fact, Tolkien chose the name directly from the ancient Old English word for the planet Venus. North Anatolian Fault Zone. The star was created when Eärendil the Mariner was set in the sky on his ship, with a Silmaril bound to his brow. Hayward Fault Zone. Tolkien, Venus is the Star of Eärendil. Calaveras Fault. R.

Alpine Fault. R. Earthquake prediction. In the mythology of Middle-earth (1937), by J. Seismic retrofit. In Olaf Stapledon's epic Last and First Men (1930), Venus is an oceanic idyll where humans evolve the power of flight. Household seismic safety. http://news.bbc.co.uk/2/hi/science/nature/3746583.stm - BBC science news.

Emergency preparedness. http://www.newscientist.com/article.ns?id=dn2843 - New Scientist article. an earthquake of 5.6 or larger every 100 years. an earthquake of 4.7 or larger every 10 years. an earthquake of 3.7 or larger every 1 year.

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