Naturally Occuring Earth Quakes

————————————————- Naturally occurring earthquakes Fault types Tectonic earthquakes occur anywhere in the earth where there is sufficient stored elastic strain energy to drive fracture propagation along a  fault plane. The sides of a fault move past each other smoothly and  aseismically  only if there are no irregularities or  asperities  along the fault surface that increase the frictional resistance. Most fault surfaces do have such asperities and this leads to a form of  stick-slip behaviour.Once the fault has locked, continued relative motion between the plates leads to increasing stress and therefore, stored strain energy in the volume around the fault surface. This continues until the stress has risen sufficiently to break through the asperity, suddenly allowing sliding over the locked portion of the fault, releasing the  stored energy. This energy is rel eased as a combination of radiated elastic  strain  seismic waves, frictional heating of the fault surface, and cracking of the rock, thus causing an earthquake.This process of gradual build-up of strain and stress punctuated by occasional sudden earthquake failure is referred to as the  elastic-rebound theory. It is estimated that only 10 percent or less of an earthquake's total energy is radiated as seismic energy. Most of the earthquake's energy is used to power the earthquake  fracture  growth or is converted into heat generated by friction. Therefore, earthquakes lower the Earth's available  elastic potential energy  and raise its temperature, though these changes are negligible compared to the conductive and convective flow of heat out from the  Earth's deep interior. 2] Earthquake fault types Main article:  Fault (geology) There are three main types of fault that may cause an earthquake: normal, reverse (thrust) and strike-slip. Normal and reverse faulting a re examples of dip-slip, where the displacement along the fault is in the direction of  dip  and movement on them involves a vertical component. Normal faults occur mainly in areas where the crust is being  extended  such as a  divergent boundary. Reverse faults occur in areas where the crust is being  shortened  such as at a convergent boundary. Strike-slip faultsare teep structures where the two sides of the fault slip horizontally past each other; transform boundaries are a particular type of strike-slip fault. Many earthquakes are caused by movement on faults that have components of both dip-slip and strike-slip; this is known as oblique slip. Reverse faults, particularly those along  convergent plate boundaries  are associated with the most powerful earthquakes, including almost all of those of magnitude 8 or more. Strike-slip faults, particularly continental  transforms  can produce major earthquakes up to about magnitude 8.Earthquakes associated with nor mal faults are generally less than magnitude 7. This is so because the energy released in an earthquake, and thus its magnitude, is proportional to the area of the fault that ruptures[3]  and the stress drop. Therefore, the longer the length and the wider the width of the faulted area, the larger the resulting magnitude. The topmost, brittle part of the Earth’s crust, and the cool slabs of the tectonic plates that are descending down into the hot mantle, are the only parts of our planet which can store elastic energy and release it in fault ruptures.Rocks hotter than about 300 degrees Celsius flow in response to stress; they do not rupture in earthquakes. [4][5]  The maximum observed lengths of ruptures and mapped faults, which may break in one go are approximately 1000  km. Examples are the earthquakes in  Chile, 1960;  Alaska, 1957;  Sumatra, 2004, all in subduction zones. The longest earthquake ruptures on strike-slip faults, like the  San Andreas Fault  (1 857, 1906), the  North Anatolian Fault  in Turkey (1939) and theDenali Fault  in Alaska (2002), are about half to one third as long as the lengths along subducting plate margins, and those along normal faults are even shorter.Aerial photo of the San Andreas Fault in the  Carrizo Plain, northwest of Los Angeles The most important parameter controlling the maximum earthquake magnitude on a fault is however not the maximum available length, but the available width because the latter varies by a factor of 20. Along converging plate margins, the dip angle of the rupture plane is very shallow, typically about 10 degrees. [6]  Thus the width of the plane within the top brittle crust of the Earth can become 50 to 100  km (Tohoku, 2011;  Alaska, 1964), making the most powerful earthquakes possible.Strike-slip faults tend to be oriented near vertically, resulting in an approximate width of 10  km within the brittle crust,[7]  thus earthquakes with magnitudes much larger than 8 are not possible. Maximum magnitudes along many normal faults are even more limited because many of them are located along spreading centers, as in Iceland, where the thickness of the brittle layer is only about 6  km. [8][9] In addition, there exists a hierarchy of stress level in the three fault types. Thrust faults are generated by the highest, strike slip by intermediate, and normal faults by the lowest stress levels. 10]  This can easily be understood by considering the direction of the greatest principal stress, the direction of the force that ‘pushes’ the rock mass during the faulting. In the case of normal faults, the rock mass is pushed down in a vertical direction, thus the pushing force (greatest  principal stress) equals the weight of the rock mass itself. In the case of thrusting, the rock mass ‘escapes’ in the direction of the least principal stress, namely upward, lifting the rock mass up, thus the overburden equals the  least  p rincipal stress.Strike-slip faulting is intermediate between the other two types described above. This difference in stress regime in the three faulting environments can contribute to differences in stress drop during faulting, which contributes to differences in the radiated energy, regardless of fault dimensions. Earthquakes away from plate boundaries Main article:  Intraplate earthquake Where plate boundaries occur within  continental lithosphere, deformation is spread out over a much larger area than the plate boundary itself.In the case of the  San Andreas fault  continental transform, many earthquakes occur away from the plate boundary and are related to strains developed within the broader zone of deformation caused by major irregularities in the fault trace (e. g. , the â€Å"Big bend† region). The  Northridge earthquake  was associated with movement on a blind thrust within such a zone. Another example is the strongly oblique convergent plate boundary bet ween the  Arabian  and  Eurasian plates  where it runs through the northwestern part of the  Zagros  mountains.The deformation associated with this plate boundary is partitioned into nearly pure thrust sense movements perpendicular to the boundary over a wide zone to the southwest and nearly pure strike-slip motion along the Main Recent Fault close to the actual plate boundary itself. This is demonstrated by earthquake  focal mechanisms. [11] All tectonic plates have internal stress fields caused by their interactions with neighbouring plates and sedimentary loading or unloading (e. g. deglaciation[12]).These stresses may be sufficient to cause failure along existing fault planes, giving rise to  intraplate earthquakes. [13] Shallow-focus and deep-focus earthquakes Main article:  Depth of focus (tectonics) The majority of tectonic earthquakes originate at the ring of fire in depths not exceeding tens of kilometers. Earthquakes occurring at a depth of less than 70  km are classified as ‘shallow-focus' earthquakes, while those with a focal-depth between 70 and 300  km are commonly termed ‘mid-focus' or ‘intermediate-depth' earthquakes.In  subduction zones, where older and colder  oceanic crust  descends beneath another tectonic plate,  deep-focus earthquakes  may occur at much greater depths (ranging from 300 up to 700  kilometers). [14]  These seismically active areas of subduction are known as  Wadati-Benioff zones. Deep-focus earthquakes occur at a depth where the subducted  lithosphere  should no longer be brittle, due to the high temperature and pressure. A possible mechanism for the generation of deep-focus earthquakes is faulting caused by  olivine  undergoing a  phase transition  into a  spinel  structure. 15] Earthquakes and volcanic activity Earthquakes often occur in volcanic regions and are caused there, both by  tectonic  faults and the movement of  magma  in  volcanoe s. Such earthquakes can serve as an early warning of volcanic eruptions, as during the  Mount St. Helens  eruption of 1980. [16]  Earthquake swarms can serve as markers for the location of the flowing magma throughout the volcanoes. These swarms can be recorded by seismometers and  tiltmeters  (a device that measures ground slope) and used as sensors to predict imminent or upcoming eruptions. [17] Rupture dynamicsA tectonic earthquake begins by an initial rupture at a point on the fault surface, a process known as nucleation. The scale of the nucleation zone is uncertain, with some evidence, such as the rupture dimensions of the smallest earthquakes, suggesting that it is smaller than 100 m while other evidence, such as a slow component revealed by low-frequency spectra of some earthquakes, suggest that it is larger. The possibility that the nucleation involves some sort of preparation process is supported by the observation that about 40% of earthquakes are preceded by fo reshocks.Once the rupture has initiated it begins to propagate along the fault surface. The mechanics of this process are poorly understood, partly because it is difficult to recreate the high sliding velocities in a laboratory. Also the effects of strong ground motion make it very difficult to record information close to a nucleation zone. [18] Rupture propagation is generally modeled using a  fracture mechanics  approach, likening the rupture to a propagating mixed mode shear crack. The rupture velocity is a function of the fracture energy in the volume around the crack tip, increasing with decreasing fracture energy.The velocity of rupture propagation is orders of magnitude faster than the displacement velocity across the fault. Earthquake ruptures typically propagate at velocities that are in the range 70–90% of the S-wave velocity and this is independent of earthquake size. A small subset of earthquake ruptures appear to have propagated at speeds greater than the S-w ave velocity. These  supershear earthquakes  have all been observed during large strike-slip events. The unusually wide zone of coseismic damage caused by the  2001 Kunlun earthquake  has been attributed to the effects of the  sonic boom  developed in such earthquakes.Some earthquake ruptures travel at unusually low velocities and are referred to as  slow earthquakes. A particularly dangerous form of slow earthquake is the  tsunami earthquake, observed where the relatively low felt intensities, caused by the slow propagation speed of some great earthquakes, fail to alert the population of the neighbouring coast, as in the  1896 Meiji-Sanriku earthquake. [18] Tidal forces See also:  Earthquake prediction#Tides Research work has shown a robust correlation between small tidally induced forces and non-volcanic tremor activity. 19][20][21][22] Earthquake clusters Most earthquakes form part of a sequence, related to each other in terms of location and time. [23]  Mos t earthquake clusters consist of small tremors that cause little to no damage, but there is a theory that earthquakes can recur in a regular pattern. [24] Aftershocks Main article:  Aftershock An aftershock is an earthquake that occurs after a previous earthquake, the mainshock. An aftershock is in the same region of the main shock but always of a smaller magnitude.If an aftershock is larger than the main shock, the aftershock is redesignated as the main shock and the original main shock is redesignated as a  foreshock. Aftershocks are formed as the crust around the displaced  fault plane  adjusts to the effects of the main shock. [23] Earthquake swarms Main article:  Earthquake swarm Earthquake swarms are sequences of earthquakes striking in a specific area within a short period of time. They are different from earthquakes followed by a series of  aftershocks  by the fact that no single earthquake in the sequence is obviously the main shock, therefore none have notabl e higher magnitudes than the other.An example of an earthquake swarm is the 2004 activity atYellowstone National Park. [25] Earthquake storms Main article:  Earthquake storm Sometimes a series of earthquakes occur in a sort of  earthquake storm, where the earthquakes strike a fault in clusters, each triggered by the shaking or stress redistribution of the previous earthquakes. Similar to  aftershocks  but on adjacent segments of fault, these storms occur over the course of years, and with some of the later earthquakes as damaging as the early ones.Such a pattern was observed in the sequence of about a dozen earthquakes that struck the  North Anatolian Fault  in Turkey in the 20th century and has been inferred for older anomalous clusters of large earthquakes in the Middle East. [26][27] ————————————————- Size and frequency of occurrence It is estimated that aro und 500,000 earthquakes occur each year, detectable with current instrumentation. About 100,000 of these can be felt. [28][29]  Minor earthquakes occur nearly constantly around the world in places like  California  and  Alaska  in the U. S. , as well as n  Mexico,  Guatemala,  Chile,  Peru,  Indonesia,  Iran,  Pakistan, the  Azores  in  Portugal,  Turkey,  New Zealand,  Greece,Italy, and  Japan, but earthquakes can occur almost anywhere, including  New York City,  London, and  Australia. [30]  Larger earthquakes occur less frequently, the relationship being  exponential; for example, roughly ten times as many earthquakes larger than magnitude 4 occur in a particular time period than earthquakes larger than magnitude 5. In the (low seismicity) United Kingdom, for example, it has been calculated that the average recurrences are: an earthquake of 3. –4. 6 every year, an earthquake of 4. 7–5. 5 every 10  years, and an earth quake of 5. 6 or larger every 100  years. [31]  This is an example of the  Gutenberg-Richter law. The  Messina earthquake  and tsunami took as many as 200,000 lives on December 28, 1908 in  Sicily  and  Calabria. [32] The number of seismic stations has increased from about 350 in 1931 to many thousands today. As a result, many more earthquakes are reported than in the past, but this is because of the vast improvement in instrumentation, rather than an increase in the number of earthquakes.The  United States Geological Survey  estimates that, since 1900, there have been an average of 18 major earthquakes (magnitude 7. 0–7. 9) and one great earthquake (magnitude 8. 0 or greater) per year, and that this average has been relatively stable. [33]  In recent years, the number of major earthquakes per year has decreased, though this is probably a statistical fluctuation rather than a systematic trend. [citation needed]  More detailed statistics on the size and frequency of earthquakes is available from the  United States Geological Survey  (USGS). 34]  A recent increase in the number of major earthquakes has been noted, which could be explained by a cyclical pattern of periods of intense tectonic activity, interspersed with longer periods of low-intensity. However, accurate recordings of earthquakes only began in the early 1900s, so it is too early to categorically state that this is the case. [35] Most of the world's earthquakes (90%, and 81% of the largest) take place in the 40,000  km long, horseshoe-shaped zone called the circum-Pacific seismic belt, known as the  Pacific Ring of Fire, which for the most part bounds the  Pacific Plate. 36][37]  Massive earthquakes tend to occur along other plate boundaries, too, such as along the  Himalayan Mountains. [38] With the rapid growth of  mega-cities  such as  Mexico City,  Tokyo  and  Tehran, in areas of high  seismic risk, some seismologists are warning that a single quake may claim the lives of up to 3  million people. [39] ————————————————- Induced seismicity Main article:  Induced seismicity While most earthquakes are caused by movement of the Earth's  tectonic plates, human activity can also produce earthquakes.Four main activities contribute to this phenomenon: storing large amounts of water behind a  dam  (and possibly building an extremely heavy  building), drilling and injecting liquid into  wells, and by  coal mining  and  oil drilling. [40]  Perhaps the best known example is the  2008 Sichuan earthquake  in China's  Sichuan Province  in May; this tremor resulted in 69,227 fatalities and is the  19th deadliest earthquake of all time. The  Zipingpu Dam  is believed to have fluctuated the pressure of the fault 1,650 feet (503  m) away; this pressure probably increased the power of t he earthquake and accelerated the rate of movement for the fault. 41]  The greatest earthquake in Australia's history is also claimed to be induced by humanity, through coal mining. The city of Newcastle  was built over a large sector of coal mining areas. The earthquake has been reported to be spawned from a fault that reactivated due to the millions of tonnes of rock removed in the mining process. [42] ————————————————- Measuring and locating earthquakes Main article:  Seismology Earthquakes can be recorded by seismometers up to great distances, because  seismic waves  travel through the whole  Earth's interior.The absolute magnitude of a quake is conventionally reported by numbers on the  Moment magnitude scale  (formerly Richter scale, magnitude 7 causing serious damage over large areas), whereas the felt magnitude is reported using the modifiedMercalli intensity scale  (intensity II–XII). Every tremor produces different types of seismic waves, which travel through rock with different velocities: * Longitudinal  P-waves  (shock- or pressure waves) * Transverse  S-waves  (both body waves) * Surface waves  Ã¢â‚¬â€ (Rayleigh  and  Love  waves) Propagation velocity  of the seismic waves ranges from approx.   km/s up to 13  km/s, depending on the  density  and  elasticity  of the medium. In the Earth's interior the shock- or P waves travel much faster than the S waves (approx. relation 1. 7  : 1). The differences in  travel time  from the  epicentre  to the observatory are a measure of the distance and can be used to image both sources of quakes and structures within the Earth. Also the depth of the  hypocenter  can be computed roughly. In solid rock P-waves travel at about 6 to 7  km per second; the velocity increases within the deep mantle to ~13  km/s.The velocity of S-waves ranges from 2–3  km/s in light sediments and 4–5  km/s in the Earth's crust up to 7  km/s in the deep mantle. As a consequence, the first waves of a distant earthquake arrive at an observatory via the Earth's mantle. Rule of thumb: On the average, the kilometer distance to the earthquake is the number of seconds between the P and S wave  times 8. [43]  Slight deviations are caused by inhomogeneities of subsurface structure. By such analyses of seismograms the Earth's core was located in 1913 by  Beno Gutenberg.Earthquakes are not only categorized by their magnitude but also by the place where they occur. The world is divided into 754  Flinn-Engdahl regions  (F-E regions), which are based on political and geographical boundaries as well as seismic activity. More active zones are divided into smaller F-E regions whereas less active zones belong to larger F-E regions. ———————————à ¢â‚¬â€Ã¢â‚¬â€Ã¢â‚¬â€Ã¢â‚¬â€Ã¢â‚¬â€- Effects of earthquakes 1755 copper engraving depicting  Lisbonin ruins and in flames after the  1755 Lisbon earthquake, which killed an estimated 60,000 people. A  tsunami  overwhelms the ships in the harbor.The effects of earthquakes include, but are not limited to, the following: Shaking and ground rupture Damaged buildings in  Port-au-Prince,Haiti, January 2010. Shaking and ground rupture are the main effects created by earthquakes, principally resulting in more or less severe damage to buildings and other rigid structures. The severity of the local effects depends on the complex combination of the earthquake  magnitude, the distance from the  epicenter, and the local geological and geomorphological conditions, which may amplify or reduce  wave propagation. [44]  The ground-shaking is measured by  ground acceleration.Specific local geological, geomorphological, and geostructural features can induce high levels of shakin g on the ground surface even from low-intensity earthquakes. This effect is called site or local amplification. It is principally due to the transfer of the  seismic  motion from hard deep soils to soft superficial soils and to effects of seismic energy focalization owing to typical geometrical setting of the deposits. Ground rupture is a visible breaking and displacement of the Earth's surface along the trace of the fault, which may be of the order of several metres in the case of major earthquakes.Ground rupture is a major risk for large engineering structures such as  dams, bridges and  nuclear power stations  and requires careful mapping of existing faults to identify any which are likely to break the ground surface within the life of the structure. [45] Landslides and avalanches Main article:  Landslide Earthquakes, along with severe storms, volcanic activity, coastal wave attack, and wildfires, can produce slope instability leading to landslides, a major geological hazard. Landslide danger may persist while emergency personnel are attempting rescue. [46] FiresFires of the  1906 San Francisco earthquake Earthquakes can cause  fires  by damaging  electrical power  or gas lines. In the event of water mains rupturing and a loss of pressure, it may also become difficult to stop the spread of a fire once it has started. For example, more deaths in the  1906 San Francisco earthquake  were caused by fire than by the earthquake itself. [47] Soil liquefaction Main article:  Soil liquefaction Soil liquefaction occurs when, because of the shaking, water-saturated  granular  material (such as sand) temporarily loses its strength and transforms from a  solid  to a  liquid.Soil liquefaction may cause rigid structures, like buildings and bridges, to tilt or sink into the liquefied deposits. This can be a devastating effect of earthquakes. For example, in the  1964 Alaska earthquake, soil liquefaction caused many buildings to sink into the ground, eventually collapsing upon themselves. [48] Tsunami The tsunami of the  2004 Indian Ocean earthquake A large ferry boat rests inland amidst destroyed houses after a 9. 0  earthquakeand subsequent tsunami struck Japan in March 2011. Main article:  Tsunami Tsunamis are long-wavelength, long-period sea waves produced by the sudden or abrupt movement of large volumes of water.In the open ocean the distance between wave crests can surpass 100 kilometers (62  mi), and the wave periods can vary from five minutes to one hour. Such tsunamis travel 600-800  kilometers per hour (373–497 miles per hour), depending on water depth. Large waves produced by an earthquake or a submarine landslide can overrun nearby coastal areas in a matter of minutes. Tsunamis can also travel thousands of kilometers across open ocean and wreak destruction on far shores hours after the earthquake that generated them. [49] Ordinarily, subduction earthquakes under magnitude 7. on the Richter scale do not cause tsunamis, although some instances of this have been recorded. Most destructive tsunamis are caused by earthquakes of magnitude 7. 5 or more. [49] Floods Main article:  Flood A flood is an overflow of any amount of water that reaches land. [50]  Floods occur usually when the volume of water within a body of water, such as a river or lake, exceeds the total capacity of the formation, and as a result some of the water flows or sits outside of the normal perimeter of the body. However, floods may be secondary effects of earthquakes, if dams are damaged.Earthquakes may cause landslips to dam rivers, which collapse and cause floods. [51] The terrain below the  Sarez Lake  in  Tajikistan  is in danger of catastrophic flood if the  landslide dam  formed by the earthquake, known as the  Usoi Dam, were to fail during a future earthquake. Impact projections suggest the flood could affect roughly 5  million people. [52] Human impacts An earthquake may cause injury and loss of life, road and bridge damage, general  property damage  (which may or may not be covered by  earthquake insurance), and collapse or destabilization (potentially leading to future collapse) of buildings.The aftermath may bring  disease, lack of basic necessities, and higher insurance premiums. ————————————————- Major earthquakes Earthquakes of magnitude 8. 0 and greater since 1900. The apparent 3D volumes of the bubbles are linearly proportional to their respective fatalities. [53] Main article:  List of earthquakes One of the most devastating earthquakes in recorded history occurred on 23 January 1556 in the  Shaanxi  province, China, killing more than 830,000 people (see  1556 Shaanxi earthquake). 54]  Most of the population in the area at the time lived in  yaodongs, artificial caves in  loess  cliffs, many of which co llapsed during the catastrophe with great loss of life. The  1976 Tangshan earthquake, with a death toll estimated to be between 240,000 to 655,000, is believed to be the largest earthquake of the 20th century by death toll. [55] The  1960 Chilean Earthquake  is the largest earthquake that has been measured on a seismograph, reaching 9. 5 magnitude on 22 May 1960. [28][29]  Its epicenter was near Canete, Chile.The energy released was approximately twice that of the next most powerful earthquake, the  Good Friday Earthquake, which was centered in  Prince William Sound, Alaska. [56][57]  The ten largest recorded earthquakes have all been  megathrust earthquakes; however, of these ten, only the  2004 Indian Ocean earthquake  is simultaneously one of the deadliest earthquakes in history. Earthquakes that caused the greatest loss of life, while powerful, were deadly because of their proximity to either heavily populated areas or the ocean, where earthquakes often crea te  tsunamis  that can devastate communities thousands of kilometers away.Regions most at risk for great loss of life include those where earthquakes are relatively rare but powerful, and poor regions with lax, unenforced, or nonexistent seismic building codes. ————————————————- Prediction Main article:  Earthquake prediction Many methods have been developed for predicting the time and place in which earthquakes will occur. Despite considerable research efforts by  seismologists, scientifically reproducible predictions cannot yet be made to a specific day or month. 58]  However, for well-understood faults the probability that a segment may rupture during the next few decades can be estimated. [59] Earthquake warning systems  have been developed that can provide regional notification of an earthquake in progress, but before the ground surface has begun to move, potentially allowing people within the system's range to seek shelter before the earthquake's impact is felt. ————————————————- Preparedness The objective of  earthquake engineering  is to foresee the impact of earthquakes on buildings and other structures and to design such structures to minimize the risk of damage.Existing structures can be modified by  seismic retrofitting  to improve their resistance to earthquakes. Earthquake insurance  can provide building owners with financial protection against losses resulting from earthquakes. Emergency management  strategies can be employed by a government or organization to mitigate risks and prepare for consequences. ————————————————- Historical views An image from a 1557 book From the lifetime of the Gre ek philosopher  Anaxagoras  in the 5th century BCE to the 14th century CE, earthquakes were usually attributed to â€Å"air (vapors) in the cavities of the Earth. [60]  Thales  of Miletus, who lived from 625–547 (BCE) was the only documented person who believed that earthquakes were caused by tension between the earth and water. [60]  Other theories existed, including the Greek philosopher Anaxamines' (585–526 BCE) beliefs that short incline episodes of dryness and wetness caused seismic activity. The Greek philosopher Democritus (460–371 BCE) blamed water in general for earthquakes. [60]  Pliny the Elder  called earthquakes â€Å"underground thunderstorms. â€Å"[60] ————————————————- Earthquakes in culture Mythology and religionIn  Norse mythology, earthquakes were explained as the violent struggling of the god  Loki. When Loki,à ‚  god  of mischief and strife, murdered  Baldr, god of beauty and light, he was punished by being bound in a cave with a poisonous serpent placed above his head dripping venom. Loki's wife  Sigyn  stood by him with a bowl to catch the poison, but whenever she had to empty the bowl the poison dripped on Loki's face, forcing him to jerk his head away and thrash against his bonds, which caused the earth to tremble. [61] In  Greek mythology,  Poseidon  was the cause and god of earthquakes.When he was in a bad mood, he struck the ground with a  trident, causing earthquakes and other calamities. He also used earthquakes to punish and inflict fear upon people as revenge. [62] In  Japanese mythology,  Namazu  (? ) is a giant  catfish  who causes earthquakes. Namazu lives in the mud beneath the earth, and is guarded by the god  Kashima  who restrains the fish with a stone. When Kashima lets his guard fall, Namazu thrashes about, causing violent earthquakes. Pop ular culture In modern  popular culture, the portrayal of earthquakes is shaped by the memory of great cities laid waste, such as  Kobe in 1995  or  San Francisco in 1906. 63]  Fictional earthquakes tend to strike suddenly and without warning. [63]  For this reason, stories about earthquakes generally begin with the disaster and focus on its immediate aftermath, as in  Short Walk to Daylight  (1972),  The Ragged Edge  (1968) or  Aftershock: Earthquake in New York  (1998). [63]  A notable example is Heinrich von Kleist's classic novella,  The Earthquake in Chile, which describes the destruction of Santiago in 1647. Haruki Murakami's short fiction collection  after the quake  depicts the consequences of the Kobe earthquake of 1995.The most popular single earthquake in fiction is the hypothetical â€Å"Big One† expected of  California's  San Andreas Fault  someday, as depicted in the novels  Richter 10  (1996) and  Goodbye California  (1977) among other works. [63]  Jacob M. Appel's widely anthologized short story,  A Comparative Seismology, features a con artist who convinces an elderly woman that an apocalyptic earthquake is imminent. [64]  In  Pleasure Boating in Lituya Bay, one of the stories in  Jim Shepard's  Like You'd Understand, Anyway, the â€Å"Big One† leads to an even more devastating tsunami.In the film  2012  (2009), solar flares (geologically implausibly) affecting the Earth's core caused massive destabilization of the Earth's crust layers. This created destruction planet-wide with earthquakes and tsunamis, foreseen by the  Mayan  culture and myth surrounding the last year noted in the  Mesoamerican calendar  Ã¢â‚¬â€Ã‚  2012. Contemporary depictions of earthquakes in film are variable in the manner in which they reflect human psychological reactions to the actual trauma that can be caused to directly afflicted families and their loved ones. 65]  Disaster mental health response research emphasizes the need to be aware of the different roles of loss of family and key community members, loss of home and familiar surroundings, loss of essential supplies and services to maintain survival. [66][67]  Particularly for children, the clear availability of caregiving adults who are able to protect, nourish, and clothe them in the aftermath of the earthquake, and to help them make sense of what has befallen them has been shown even more important to their emotional and physical health than the simple giving of provisions. 68]  As was observed after other disasters involving destruction and loss of life and their media depictions, such as those of the 2001 World Trade Center Attacks or Hurricane Katrina—and has been recently observed in the  2010 Haiti earthquake, it is also important not to pathologize the reactions to loss and displacement or disruption of governmental administration and services, but rather to validate these reactions, to support constructive problem-solving and reflection as to how one might improve the conditions of those affected. [69]