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92-697: This list is ordered from source to mouth: Prads-Haute-Bléone , La Javie , Le Brusquet , Marcoux , Digne-les-Bains , Aiglun , Mallemoisson , Le Chaffaut-Saint-Jurson , Mirabeau , Malijai , L'Escale , Les Mées , This Alpes-de-Haute-Provence geographical article is a stub . You can help Misplaced Pages by expanding it . This article related to a river in France is a stub . You can help Misplaced Pages by expanding it . Prads-Haute-Bl%C3%A9one Prads-Haute-Bléone ( French pronunciation: [pʁats ot bleɔn] ; Prats Auta Blèuna in Vivaro-Alpine )

184-468: A primary education to boys. No instruction was given to girls, nor under the Falloux Laws of 1851, which required the opening of a girls school in the communes with more than 800 inhabitants, nor did the first Duruy Law (1867), which lowered the threshold to 500 inhabitants, concern Blegiers. The commune took advantage of subsidies from the second Duruy Law (1877) to build new schools everywhere. Only

276-729: A tsunami . Earthquakes can trigger landslides . Earthquakes' occurrence is influenced by tectonic movements along faults, including normal, reverse (thrust), and strike-slip faults, with energy release and rupture dynamics governed by the elastic-rebound theory . Efforts to manage earthquake risks involve prediction, forecasting, and preparedness, including seismic retrofitting and earthquake engineering to design structures that withstand shaking. The cultural impact of earthquakes spans myths, religious beliefs, and modern media, reflecting their profound influence on human societies. Similar seismic phenomena, known as marsquakes and moonquakes , have been observed on other celestial bodies, indicating

368-614: A charter which aims to "contribute to the conservation and the animation of the economic and social fabric in rural areas by maintaining a place in village life" . There is also a centre for excursions and hikes. In ancient times , Bodiontiques ( Bodiontici ) lived in the Valley of the Bléone , and were therefore the Gallic people who lived in the valleys of the current commune of Prads-Haute-Bléone. The Bodiontiques, who were defeated by Augustus at

460-571: A depth of less than 70 km (43 mi) are classified as "shallow-focus" earthquakes, while those with a focal depth between 70 and 300 km (43 and 186 mi) 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 to 700 km (190 to 430 mi)). These seismically active areas of subduction are known as Wadati–Benioff zones . Deep-focus earthquakes occur at

552-488: 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. Earthquakes often occur in volcanic regions and are caused there, both by tectonic faults and the movement of magma in volcanoes . Such earthquakes can serve as an early warning of volcanic eruptions, as during

644-475: A few exceptions to this: Supershear earthquake ruptures are known to have propagated at speeds greater than the S wave velocity. These have so far all been observed during large strike-slip events. The unusually wide zone of damage caused by the 2001 Kunlun earthquake has been attributed to the effects of the sonic boom developed in such earthquakes. Slow earthquake ruptures travel at unusually low velocities. A particularly dangerous form of slow earthquake

736-469: A flow was triggered resulting in a blackish marl-limestone detrital mass and marl-shale colluvium . If the distance travelled by the flow is reduced (700 m), it carries large blocks and upon arrival, the materials and the largest blocks are very close to the hamlet the entire flow remaining in an unstable state. The name of the village, as it appears for the first time the 9th century ( Colonia in Prato )

828-470: A meter) limestone and shale marl. The commune is crossed by the Bléone and Galabre . The commune has 7,500 hectares (19,000 acres) of woods and forests, or 45% of its area. With respect to seismic activity , the area of Prads-Haute-Bléone is in zone 4 (medium risk) according to the probabilistic classification EC8 of 2011. The municipality of Prads-Haute-Bléone is also exposed to three other natural hazards: The municipality of Prads-Haute-Bléone

920-603: A particular location in the Earth is the average rate of seismic energy release per unit volume. One of the most devastating earthquakes in recorded history was the 1556 Shaanxi earthquake , which occurred on 23 January 1556 in Shaanxi , China. More than 830,000 people died. Most houses in the area were yaodongs —dwellings carved out of loess hillsides—and many victims were killed when these structures collapsed. The 1976 Tangshan earthquake , which killed between 240,000 and 655,000 people,

1012-402: A particular time. The seismicity at a particular location in the Earth is the average rate of seismic energy release per unit volume. In its most general sense, the word earthquake is used to describe any seismic event that generates seismic waves. Earthquakes can occur naturally or be induced by human activities, such as mining , fracking , and nuclear tests . The initial point of rupture

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1104-730: A single rupture) are approximately 1,000 km (620 mi). Examples are the earthquakes in Alaska (1957) , Chile (1960) , and Sumatra (2004) , all in subduction zones. The longest earthquake ruptures on strike-slip faults, like the San Andreas Fault ( 1857 , 1906 ), the North Anatolian Fault in Turkey ( 1939 ), and the Denali Fault in Alaska ( 2002 ), are about half to one third as long as

1196-611: A succession crisis in the Comté de Provence  [ fr ] , the towns of the Union of Aix (1382-1387), supported Charles, Duke of Durazzo against Louis I, Duke of Anjou . The Lord of Chanolles, Louis le Roux, supported the Duke of Anjou as early as April 1382, this support was conditional on the participation of the Duke in the relief expedition to the Queen. The Lord of Blegiers, Louis Aymes, appears in

1288-410: A zone of talus), in l'Adret and located beneath the summit of Belle Valette. In the autumn of 1967, already marked by heavy rains, the cracks in the ground expanded. During the winter of 1967–1968, the successions of freeze-thaw lubricated the sliding surfaces. The rainy spring only aggravated the instability of the land. During the autumn 1968 rains, more than a year after the start of the sequence,

1380-558: Is a commune in the Alpes-de-Haute-Provence department and in the Provence-Alpes-Côte d'Azur region in southeastern France. The people of Prads-Haute-Bléone are called Pradins. The neighboring communes of Prads-Haute-Bléone are Méolans-Revel , Allos , Villars-Colmars , Thorame-Basse , Draix , La Javie , Beaujeu and Verdaches . The village lies on the right bank of the Bléone , which has its source in

1472-515: Is a theory that earthquakes can recur in a regular pattern. Earthquake clustering has been observed, for example, in Parkfield, California where a long-term research study is being conducted around the Parkfield earthquake cluster. An aftershock is an earthquake that occurs after a previous earthquake, the mainshock. Rapid changes of stress between rocks, and the stress from the original earthquake are

1564-410: Is called the hypocenter or focus, while the ground level directly above it is the epicenter . Earthquakes are primarily caused by geological faults , but also by volcanic activity , landslides, and other seismic events. The frequency, type, and size of earthquakes in an area define its seismic activity, reflecting the average rate of seismic energy release. Significant historical earthquakes include

1656-520: 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. There are three main types of fault, all of which may cause an interplate earthquake : normal, reverse (thrust), and strike-slip. Normal and reverse faulting are examples of dip-slip, where

1748-543: Is derived from the Latin pratum (pré). The plural is recent. The Bléone name means Wolf River . Mariaud appears in the texts at the beginning of the 13th century, but in the form of Mariano : According to Ernest Nègre , the place name derived from the proper Roman name of Marianus , which has evolved from Mariaudo (1319), by attraction to the Provençal local maridado , meaning wedding. Other hypotheses exist. Blegiers

1840-400: 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. Standard reporting of earthquakes includes its magnitude , date and time of occurrence, geographic coordinates of its epicenter , depth of

1932-528: Is exposed to any of the risks of technological origin identified by the prefecture. The predictable natural risk prevention plan  [ fr ] (PPR) of the municipality was approved in 1993 for the risk of land movement; the DICRIM  [ fr ] does not exist. The commune was the subject to an avalanche, in 2009. In July 2005, the municipality also had significant mudslides after heavy rains. The following list includes earthquakes felt strongly in

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2024-511: Is mentioned for the first time in charters in the second decade of the 12th century, in the form de Bligerio , derived from the Germanic name Blidegar , possibly Latinized as Blidegarius . Chanolles , cited in 1122 ( Canola ), comes from the Pre-Celtic oronym (mountain toponym) *Kan- . The name of the summit of Chappe at 1,667 metres (5,469 ft), bordering on Beaujeu , is maintained in

2116-532: Is probably a statistical fluctuation rather than a systematic trend. More detailed statistics on the size and frequency of earthquakes is available from the United States Geological Survey. 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

2208-423: Is proportional to the area of the fault that ruptures and the stress drop. Therefore, the longer the length and the wider the width of the faulted area, the larger the resulting magnitude. The most important parameter controlling the maximum earthquake magnitude on a fault, however, is not the maximum available length, but the available width because the latter varies by a factor of 20. Along converging plate margins,

2300-410: 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 neighboring coast, as in the 1896 Sanriku earthquake . During an earthquake, high temperatures can develop at the fault plane, increasing pore pressure and consequently vaporization of the groundwater already contained within

2392-672: Is the construction of a public fountain in the village, under the Second Republic , in 1850. The coup d'état of 2 December 1851 by Louis-Napoléon Bonaparte against the Second Republic caused an armed uprising in the Basses-Alpes, in defense of the constitution. After the failure of the uprising, severe repression descended on those who stood up to defend the Republic, which included an inhabitant of Prads. As with many municipalities of

2484-501: The 1556 Shaanxi earthquake in China, with over 830,000 fatalities, and the 1960 Valdivia earthquake in Chile, the largest ever recorded at 9.5 magnitude. Earthquakes result in various effects, such as ground shaking and soil liquefaction , leading to significant damage and loss of life. When the epicenter of a large earthquake is located offshore, the seabed may be displaced sufficiently to cause

2576-400: The 1980 eruption of Mount St. Helens . 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. A tectonic earthquake begins as an area of initial slip on the fault surface that forms

2668-587: 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 create 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. Tectonic earthquakes occur anywhere on

2760-652: The Abbey of Saint Victor in Marseille had a Cour colongère  [ fr ] . The two communities of Chanolles and Champourcin which had eight feus each count of 1315, were heavily depopulated by the crises of the 14th century (the Black Death and the Hundred Years' War ), and were annexed by Blegiers in the 15th century. Champourcin and Chanolles churches were of the chapter of Digne. The death of Queen Jeanne I opened

2852-657: The Chapter of Digne that owned the domain and the Church of the Roche-de-Blégiers, before selling these in 1476 to the Bishop of Digne  [ fr ] . From that date, it was the Bishop who appointed the responsible chaplain of the souls of this parish, and who collects revenues attached to this church. Chanolles was reported as early as 814: The Polyptych of Wadalde indicated that

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2944-571: The Cluny Abbey , and then passes under the authority of the college Saint-Martial in Avignon . The abbey was eventually looted, ransacked and abandoned during the French Wars of Religion . The tithes were levied by the Chapter of Digne . In 1843, the priest of the parish, Paul Charpenel, writes the annals of the parish of Prads, not published to date. One of the municipal measures from this period

3036-490: The Himalayan Mountains . 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 earthquake may claim the lives of up to three million people. While most earthquakes are caused by the movement of the Earth's tectonic plates , human activity can also produce earthquakes. Activities both above ground and below may change

3128-585: The Massif des Trois-Évêchés at the border with Méolans-Revel. This is also the highest summit of the Provence Alps and Prealps . It is common with the type of high valleys of the Southern Alps, enjoying a climate which is very sunny, cold, dry, and with a snow line at approximately 1,800 metres (5,900 ft). During the two last major glaciations, Riss glaciation and Würm glaciation , major glaciers occupied

3220-565: The Second Empire . It is only since the Ferry Laws that Prads girls have attended school regularly. In the Middle Ages , during the 12th century, the village of Blégiers ( Bligerium ) moved to the Roche-de-Blégiers, on a hilltop site. The community had a consulate in the 13th century. Its population increased from 81 feus in 1315, with another 14 in 1471. At this time, it was still part of

3312-426: The brittle-ductile transition zone and upwards by the ground surface. The mechanics of this process are poorly understood because it is difficult either to recreate such rapid movements in a laboratory or to record seismic waves close to a nucleation zone due to strong ground motion. In most cases, the rupture speed approaches, but does not exceed, the shear wave (S wave) velocity of the surrounding rock. There are

3404-413: The least principal 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. For every unit increase in magnitude, there is a roughly thirty-fold increase in

3496-541: The 20th century and has been inferred for older anomalous clusters of large earthquakes in the Middle East. It is estimated that around 500,000 earthquakes occur each year, detectable with current instrumentation. About 100,000 of these can be felt. Minor earthquakes occur very frequently around the world in places like California and Alaska in the U.S., as well as in El Salvador, Mexico, Guatemala, Chile, Peru, Indonesia,

3588-475: The 20th century. In 2013, a new artisanal sawmill was created in the village of Blegiers. At the end of 2015, the tertiary sector (shops, transport, services) had eight institutions (one salaried employee), in addition to seven institutions in the administrative sector (together with the health and social sector and education), with six people employed. According to the Observatoire départemental du tourisme ,

3680-433: The 21st century. Seismic waves travel through the Earth's interior and can be recorded by seismometers at great distances. The surface-wave magnitude was developed in the 1950s as a means to measure remote earthquakes and to improve the accuracy for larger events. The moment magnitude scale not only measures the amplitude of the shock but also takes into account the seismic moment (total rupture area, average slip of

3772-535: The Blegiers school was renovated. It is only with the Ferry Laws that girls became educated regularly. While the settlement was isolated, polyculture allowed most of the needs to be met. Wine was produced locally, but had a poor reputation. A polyculture, the highest in the Bléone Valley, was abandoned before World War I . The decline of self-sufficient polyculture continued after World War II, and harvesting wheat

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3864-399: The Earth's core was located in 1913 by Beno Gutenberg . S waves and later arriving surface waves do most of the damage compared to P waves. P waves squeeze and expand the material in the same direction they are traveling, whereas S waves shake the ground up and down and back and forth. Earthquakes are not only categorized by their magnitude but also by the place where they occur. The world

3956-481: The Earth. Also, the depth of the hypocenter can be computed roughly. P wave speed S waves speed As a consequence, the first waves of a distant earthquake arrive at an observatory via the Earth's mantle. On average, the kilometer distance to the earthquake is the number of seconds between the P- and S wave times 8. Slight deviations are caused by inhomogeneities of subsurface structure. By such analysis of seismograms,

4048-558: The Philippines, Iran, Pakistan, the Azores in Portugal, Turkey, New Zealand, Greece, Italy, India, Nepal, and Japan. Larger earthquakes occur less frequently, the relationship being exponential ; for example, roughly ten times as many earthquakes larger than magnitude 4 occur than earthquakes larger than magnitude 5. In the (low seismicity) United Kingdom, for example, it has been calculated that

4140-463: The average recurrences are: an earthquake of 3.7–4.6 every year, an earthquake of 4.7–5.5 every 10 years, and an earthquake of 5.6 or larger every 100 years. This is an example of the Gutenberg–Richter law . 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

4232-404: The brittle crust. Thus, earthquakes with magnitudes much larger than 8 are not possible. In addition, there exists a hierarchy of stress levels in the three fault types. Thrust faults are generated by the highest, strike-slip by intermediate, and normal faults by the lowest stress levels. This can easily be understood by considering the direction of the greatest principal stress, the direction of

4324-555: The cause of other earthquakes in the past century. A Columbia University paper suggested that the 8.0 magnitude 2008 Sichuan earthquake was induced by loading from the Zipingpu Dam , though the link has not been conclusively proved. The instrumental scales used to describe the size of an earthquake began with the Richter scale in the 1930s. It is a relatively simple measurement of an event's amplitude, and its use has become minimal in

4416-559: The commune (52%). At the end of 2015, the primary sector (agriculture, forestry, fishing) had 14 active institutions within the meaning of Insee (including non-professional operators and self-employment). The number of professional farms, according to the Agreste survey of the Ministry of Agriculture, is nine in 2010. It was 11 in 2000, and 18 in 1988. Currently, these operators are divided into sheep and vegetable farmers. From 1988 to 2000,

4508-500: The department, Prads acquired schools well before the Jules Ferry laws : in 1863, it had three, located in Prads, la Favière and Tercier. These schools provided a primary education to boys. While the Falloux Laws of 1851, required the opening of a girls school in communes with more than 800 inhabitants, Prads maintained a girls school in the 1860s, but that school closed before the end of

4600-521: The dip angle of the rupture plane is very shallow, typically about 10 degrees. Thus, the width of the plane within the top brittle crust of the Earth can reach 50–100 km (31–62 mi) (such as in Japan, 2011 , or in Alaska, 1964 ), making the most powerful earthquakes possible. The majority of tectonic earthquakes originate in the Ring of Fire at depths not exceeding tens of kilometers. Earthquakes occurring at

4692-678: The displacement along the fault is in the direction of dip and where movement on them involves a vertical component. Many earthquakes are caused by movement on faults that have components of both dip-slip and strike-slip; this is known as oblique slip. The topmost, brittle part of the Earth's crust, and the cool slabs of the tectonic plates that are descending into the hot mantle, are the only parts of our planet that can store elastic energy and release it in fault ruptures. Rocks hotter than about 300 °C (572 °F) flow in response to stress; they do not rupture in earthquakes. The maximum observed lengths of ruptures and mapped faults (which may break in

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4784-439: The distance from the earthquake and the underlying rock or soil makeup. The first scale for measuring earthquake magnitudes was developed by Charles Francis Richter in 1935. Subsequent scales ( seismic magnitude scales ) have retained a key feature, where each unit represents a ten-fold difference in the amplitude of the ground shaking and a 32-fold difference in energy. Subsequent scales are also adjusted to have approximately

4876-543: The early 1900s, so it is too early to categorically state that this is the case. Most of the world's earthquakes (90%, and 81% of the largest) take place in the 40,000-kilometre-long (25,000 mi), 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 . Massive earthquakes tend to occur along other plate boundaries too, such as along

4968-403: 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 increases the frictional resistance. Most fault surfaces do have such asperities, which leads to a form of stick-slip behavior . Once

5060-426: 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, 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

5152-498: The energy released. For instance, an earthquake of magnitude 6.0 releases approximately 32 times more energy than a 5.0 magnitude earthquake and a 7.0 magnitude earthquake releases 1,000 times more energy than a 5.0 magnitude earthquake. An 8.6-magnitude earthquake releases the same amount of energy as 10,000 atomic bombs of the size used in World War II . This is so because the energy released in an earthquake, and thus its magnitude,

5244-467: The existence of an optical telegraph relay, known as Télégraphe Chappe  [ fr ] . The name of the locality of la Favière evokes a planted field of beans ( fèves  [ fr ] ); that of Combes designates a ravine (similar to combe ), downstream of the village of Prads. In 2017, the active population amounted to 69 people, including 10 unemployed. These workers are in majority employees (68%), and are in majority employed outside

5336-458: The fact that no single earthquake in the sequence is the main shock, so none has a notably higher magnitude than another. An example of an earthquake swarm is the 2004 activity at Yellowstone National Park . In August 2012, a swarm of earthquakes shook Southern California 's Imperial Valley , showing the most recorded activity in the area since the 1970s. Sometimes a series of earthquakes occur in what has been called an earthquake storm , where

5428-462: 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 released as a combination of radiated elastic strain seismic waves , frictional heating of

5520-411: The fault plane that holds it in place, and fluids can exert a lubricating effect. As thermal overpressurization may provide positive feedback between slip and strength fall at the fault plane, a common opinion is that it may enhance the faulting process instability. After the mainshock, the pressure gradient between the fault plane and the neighboring rock causes a fluid flow that increases pore pressure in

5612-418: 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

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5704-536: The fault, and rigidity of the rock). The Japan Meteorological Agency seismic intensity scale , the Medvedev–Sponheuer–Karnik scale , and the Mercalli intensity scale are based on the observed effects and are related to the intensity of shaking. The shaking of the earth is a common phenomenon that has been experienced by humans from the earliest of times. Before the development of strong-motion accelerometers,

5796-417: The focus. Once the rupture has been initiated, it begins to propagate away from the focus, spreading out along the fault surface. Lateral propagation will continue until either the rupture reaches a barrier, such as the end of a fault segment, or a region on the fault where there is insufficient stress to allow continued rupture. For larger earthquakes, the depth extent of rupture will be constrained downwards by

5888-406: 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, and thus, the overburden equals

5980-410: The intensity of a seismic event was estimated based on the observed effects. Magnitude and intensity are not directly related and calculated using different methods. The magnitude of an earthquake is a single value that describes the size of the earthquake at its source. Intensity is the measure of shaking at different locations around the earthquake. Intensity values vary from place to place, depending on

6072-502: The junction of the dioceses of Digne , Senez , and Embrun . The Abbey of Cistercian monks of Notre-Dame de Faillefeu (or meadows: the Abbot was called "the Abbot of the meadows") was founded in 1144 by the monks of Boscodon  [ fr ] . They founded the Abbey of Valbonne  [ fr ] on 3 February 1199 (the date of the Charter of Foundation). In 1298, it belongs to

6164-471: The lengths along subducting plate margins, and those along normal faults are even shorter. Normal faults occur mainly in areas where the crust is being extended such as a divergent boundary . Earthquakes associated with normal faults are generally less than magnitude 7. Maximum magnitudes along many normal faults are even more limited because many of them are located along spreading centers, as in Iceland, where

6256-578: The lists of support to the Angevins in 1385, after the death of Louis I. In 1765, Blégiers had 257 inhabitants. The lordship of the place had belonged successively to the Grimaldi (14th century), Puget and Eissautier families. As Prads, Blégiers acquired schools well before the Jules Ferry laws : In 1863, it had four installed in Blégiers and the villages of Heyres, Chanolles and Chavailles. These schools provided

6348-402: The main causes of these aftershocks, along with the crust around the ruptured fault plane as it adjusts to the effects of the mainshock. An aftershock is in the same region as the main shock but always of a smaller magnitude, however, they can still be powerful enough to cause even more damage to buildings that were already previously damaged from the mainshock. If an aftershock is larger than

6440-414: The mainshock, the aftershock is redesignated as the mainshock 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 mainshock. Earthquake swarms are sequences of earthquakes striking in a specific area within a short period. They are different from earthquakes followed by a series of aftershocks by

6532-449: The northeastern part of the commune and flows southwest through the middle of the commune. The municipality of Prads-Haute-Bléone extends over 16,500 hectares (41,000 acres). It is composed of nine hamlets ranging in elevation from 800 to 1,450 metres. The main settlement of Prads is at 1,048 metres (3,438 ft), and the highest peak is the Tête de l'Estrop at 2,961 metres (9,715 ft) in

6624-518: The rock. In the coseismic phase, such an increase can significantly affect slip evolution and speed, in the post-seismic phase it can control the Aftershock sequence because, after the main event, pore pressure increase slowly propagates into the surrounding fracture network. From the point of view of the Mohr-Coulomb strength theory , an increase in fluid pressure reduces the normal stress acting on

6716-437: The rupture of geological faults but also by other events such as volcanic activity, landslides, mine blasts, fracking and nuclear tests . An earthquake's point of initial rupture is called its hypocenter or focus. The epicenter is the point at ground level directly above the hypocenter. The seismic activity of an area is the frequency, type, and size of earthquakes experienced over a particular time. The seismicity at

6808-522: The same numeric value within the limits of the scale. Although the mass media commonly reports earthquake magnitudes as "Richter magnitude" or "Richter scale", standard practice by most seismological authorities is to express an earthquake's strength on the moment magnitude scale, which is based on the actual energy released by an earthquake, the static seismic moment. Every earthquake produces different types of seismic waves, which travel through rock with different velocities: Propagation velocity of

6900-702: The same time as other peoples present on the Trophy of the Alps (before 14 BC) are attached to the Roman province of Alpes Maritimae at its inception. The communities of Blegiers, Champourcin, Chanolles, Chavailles, Mariaud and Prads were all of the Bailli of Digne . The locality of Prads appears for the first time in charters in the High Middle Ages , as Prato , dependent upon the Abbey of Saint Victor in Marseille . It stood at

6992-464: The seismic waves through solid rock ranges from approx. 3 km/s (1.9 mi/s) up to 13 km/s (8.1 mi/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 epicenter to the observatory are a measure of the distance and can be used to image both sources of earthquakes and structures within

7084-449: The shaking of the Earth 's surface resulting from a sudden release of energy in the lithosphere that creates seismic waves . Earthquakes can range in intensity , from those so weak they cannot be felt, to those violent enough to propel objects and people into the air, damage critical infrastructure, and wreak destruction across entire cities. The seismic activity of an area is the frequency, type, and size of earthquakes experienced over

7176-733: The southern entrance to the town (Champourcin, Chanolles, Blegiers) are situated in limestone mountains of the Jurassic period. Further upstream and to left bank of the Bléone , the Carton and the Chau ridges are more recent limestone formations of the Upper Cretaceous . In front of these formations at the right bank, the Galabre ridge which separates the Bléone Valley is composed of Bathonian limestone. This has beds of marl , alternating with shallow (less than

7268-422: The stresses and strains on the crust, including building reservoirs, extracting resources such as coal or oil, and injecting fluids underground for waste disposal or fracking . Most of these earthquakes have small magnitudes. The 5.7 magnitude 2011 Oklahoma earthquake is thought to have been caused by disposing wastewater from oil production into injection wells , and studies point to the state's oil industry as

7360-604: The succession of Jeanne I , the Lord of Mariaud, Gui de Saint-Marcial, supported Louis as the Duke of Anjou from the spring of 1382. It had 195 inhabitants in 1765. As Prads and Blégiers, Mariaud acquired a school well before the Jules Ferry laws, for the hamlet of Vière. Also as with Blégiers and Prads, no instruction was given to girls by the Falloux Laws of 1851, and nor did the first Duruy Laws of 1867 apply to Mariaud. Again, it

7452-490: The surrounding fracture networks; such an increase may trigger new faulting processes by reactivating adjacent faults, giving rise to aftershocks. Analogously, artificial pore pressure increase, by fluid injection in Earth's crust, may induce seismicity . Tides may trigger some seismicity . Most earthquakes form part of a sequence, related to each other in terms of location and time. Most earthquake clusters consist of small tremors that cause little to no damage, but there

7544-443: The thickness of the brittle layer is only about six kilometres (3.7 mi). Reverse faults occur in areas where the crust is being shortened such as at a convergent boundary . Reverse faults, particularly those along convergent boundaries, are associated with the most powerful earthquakes (called megathrust earthquakes ) including almost all of those of magnitude 8 or more. Megathrust earthquakes are responsible for about 90% of

7636-461: The total seismic moment released worldwide. Strike-slip faults are steep structures where the two sides of the fault slip horizontally past each other; transform boundaries are a particular type of strike-slip fault. Strike-slip faults, particularly continental transforms , can produce major earthquakes up to about magnitude 8. Strike-slip faults tend to be oriented near vertically, resulting in an approximate width of 10 km (6.2 mi) within

7728-496: The tourist function is very important for the municipality, with more than five tourists accommodated per capita, despite a low capacity of accommodation for tourist purposes: Secondary residences complement the capacity: with a number of 212, they represent 65% of dwellings. The bistro at the Trois Évêchés, which carries the Bistrot de Pays  [ fr ] brand, adheres to

7820-522: The town. They exceed a macro-seismic intensity level V on the MSK scale (sleepers awake, falling objects). The specified intensities are those felt in the town, the intensity can be stronger at the epicentre : On 5 and 6 November 1968, Prads had one of the first landslides of magnitude which was studied in detail by geomorphologists. It was produced in the Ravin de la Frache (an Occitan term that precisely refers to

7912-505: The universality of such events beyond Earth. An earthquake is the shaking of the surface of Earth resulting from a sudden release of energy in the lithosphere that creates seismic waves . Earthquakes may also be referred to as quakes , tremors , or temblors . The word tremor is also used for non-earthquake seismic rumbling . In its most general sense, an earthquake is any seismic event—whether natural or caused by humans—that generates seismic waves. Earthquakes are caused mostly by

8004-608: The usable agricultural land (SAU) had significantly increased, from 943 hectares (2,330 acres) to 1,426 hectares (3,520 acres). The SAU has dropped during the last decade, to 589 hectares (1,460 acres). At the end of 2015, the secondary sector (industry and construction) had 8 establishments, employing one worker. The hydroelectric power plant of Chanolles used the waters of the Bléone . The turbine had an output of 210 kW . Formerly, hydropower sawmills were installed in Champourcin, Blegiers and Prads. They all ceased operation in

8096-523: The valleys of the commune. A first glacier, reduced, occupied the top of the Valley of the Galebre (formerly commune of Mariaud). A great glacier flowed into the Bléone Valley; It received tributaries from the glacier valleys of the ravine of Bussing, Riou and the ravine of Jet des Eaux and Riou de l’Aune. The Riss glacier descended to Blegiers; the Würm glaciation was less thick and stopped below Heyre. The valleys of

8188-436: The vast improvement in instrumentation, rather than an increase in the number of earthquakes. The United States Geological Survey (USGS) 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. In recent years, the number of major earthquakes per year has decreased, though this

8280-502: Was stopped in 1958. The community of Mariaud appears in texts in 1218 ( Mariaudum ). With a consul from 1237, it had 50 feus in 1315, but only 10 by 1471. The Church of Mariaud reported to the Abbey of Saint-Ruf  [ fr ] in Valence , but it was the Prior of Beaujeu , who collected the tithe . In the conflict between Charles, Duke of Durazzo and Louis I, Duke of Anjou in

8372-626: Was the deadliest of the 20th century. The 1960 Chilean earthquake is the largest earthquake that has been measured on a seismograph, reaching 9.5 magnitude on 22 May 1960. Its epicenter was near Cañete, Chile. The energy released was approximately twice that of the next most powerful earthquake, the Good Friday earthquake (27 March 1964), which was centered in Prince William Sound , Alaska. The ten largest recorded earthquakes have all been megathrust earthquakes ; however, of these ten, only

8464-495: Was with the Ferry Laws that Mariaud girls became educated regularly. In 1939, after displacement of the village, the main settlement became Vière at Saume Longue. During the French Revolution , the communes of Blegiers and Prads each had a patriotic society, both created after the end of 1792. Seismic activity An earthquake  – also called a quake , tremor , or temblor  – is

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