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- El peligro sísmico (o peligrosidad sísmica) de una región se denomina a la probabilidad de que se produzcan en ella movimientos sísmicos de una cierta importancia en un plazo determinado. No debe confundirse este concepto con el de riesgo sísmico, que depende de factores antrópicos y se refiere a los daños potenciales. (es)
- L'aléa sismique est la probabilité qu'un séisme destructeur de caractéristiques données (exprimées en général par des paramètres tels que l’accélération, la période de récurrence, l’intensité, le spectre de réponse…) se produise dans une région donnée pendant une période donnée. Il ne doit pas être confondu avec le risque sismique qui est la probabilité qu'un séisme engendre des destructions et fasse des victimes. Ce risque est une combinaison de « l'aléa sismique, la concentration des biens et des personnes et la vulnérabilité des infrastructures ». L'évaluation de l'aléa peut se faire par une méthode déterministe ou probabiliste de prévision sismique. « Dans le premier cas, les caractéristiques sont celle d’un évènement réel, éventuellement assortie d’une marge de sécurité (séisme le plus fort connu historiquement par exemple). Dans l’approche probabiliste, l’ensemble des données permettant l’estimation de l’aléa sont examinées dans un cadre statistique, et l’aléa est alors exprimé comme une probabilité de dépasser un niveau fixé. » (fr)
- A seismic hazard is the probability that an earthquake will occur in a given geographic area, within a given window of time, and with ground motion intensity exceeding a given threshold. With a hazard thus estimated, risk can be assessed and included in such areas as building codes for standard buildings, designing larger buildings and infrastructure projects, land use planning and determining insurance rates. The seismic hazard studies also may generate two standard measures of anticipated ground motion, both confusingly abbreviated MCE; the simpler probabilistic Maximum Considered Earthquake (or Event ), used in standard building codes, and the more detailed and deterministic Maximum Credible Earthquake incorporated in the design of larger buildings and civil infrastructure like dams or bridges. It is important to clarify which MCE is being discussed. Calculations for determining seismic hazard were first formulated by C. Allin Cornell in 1968 and, depending on their level of importance and use, can be quite complex. The regional geology and seismology setting is first examined for sources and patterns of earthquake occurrence, both in depth and at the surface from seismometer records; secondly, the impacts from these sources are assessed relative to local geologic rock and soil types, slope angle and groundwater conditions. Zones of similar potential earthquake shaking are thus determined and drawn on maps. The well known San Andreas Fault is illustrated as a long narrow elliptical zone of greater potential motion, like many areas along continental margins associated with the Pacific ring of fire. Zones of higher seismicity in the continental interior may be the site for intraplate earthquakes) and tend to be drawn as broad areas, based on historic records, like the 1812 New Madrid earthquake, since specific causative faults are generally not identified as earthquake sources. Each zone is given properties associated with source potential: how many earthquakes per year, the maximum size of earthquakes (maximum magnitude), etc. Finally, the calculations require formulae that give the required hazard indicators for a given earthquake size and distance. For example, some districts prefer to use peak acceleration, others use peak velocity, and more sophisticated uses require response spectral ordinates. The computer program then integrates over all the zones and produces probability curves for the key ground motion parameter. The final result gives a 'chance' of exceeding a given value over a specified amount of time. Standard building codes for homeowners might be concerned with a 1 in 500 years chance, while nuclear plants look at the 10,000 year time frame. A longer-term seismic history can be obtained through paleoseismology. The results may be in the form of a ground response spectrum for use in seismic analysis. More elaborate variations on the theme also look at the soil conditions. Higher ground motions are likely to be experienced on a soft swamp compared to a hard rock site. The standard seismic hazard calculations become adjusted upwards when postulating characteristic earthquakes. Areas with high ground motion due to soil conditions are also often subject to soil failure due to liquefaction. Soil failure can also occur due to earthquake-induced landslides in steep terrain. Large area landsliding can also occur on rather gentle slopes as was seen in the Good Friday earthquake in Anchorage, Alaska, March 28, 1964. (en)
- Sebbene di gran lunga confuso con il rischio sismico il pericolo sismico è lo studio dei movimenti del suolo del terremoto previsto in ogni punto della terra finalizzato alla stima dell'intensità massima prevista del sisma su una determinata zona. Quando si costruisce un edificio, le del pericolo sismico sono usate per cercare il migliore (o il peggiore) posto dove è possibile localizzare la scossa provocata da un terremoto. Mappa del movimento di superficie per un ipotetico terremoto nella parte nord della zona della e la sua presunta estensione verso nord, la zona della (it)
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| rdfs:comment
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- El peligro sísmico (o peligrosidad sísmica) de una región se denomina a la probabilidad de que se produzcan en ella movimientos sísmicos de una cierta importancia en un plazo determinado. No debe confundirse este concepto con el de riesgo sísmico, que depende de factores antrópicos y se refiere a los daños potenciales. (es)
- Sebbene di gran lunga confuso con il rischio sismico il pericolo sismico è lo studio dei movimenti del suolo del terremoto previsto in ogni punto della terra finalizzato alla stima dell'intensità massima prevista del sisma su una determinata zona. Quando si costruisce un edificio, le del pericolo sismico sono usate per cercare il migliore (o il peggiore) posto dove è possibile localizzare la scossa provocata da un terremoto. Mappa del movimento di superficie per un ipotetico terremoto nella parte nord della zona della e la sua presunta estensione verso nord, la zona della (it)
- L'aléa sismique est la probabilité qu'un séisme destructeur de caractéristiques données (exprimées en général par des paramètres tels que l’accélération, la période de récurrence, l’intensité, le spectre de réponse…) se produise dans une région donnée pendant une période donnée. Il ne doit pas être confondu avec le risque sismique qui est la probabilité qu'un séisme engendre des destructions et fasse des victimes. Ce risque est une combinaison de « l'aléa sismique, la concentration des biens et des personnes et la vulnérabilité des infrastructures ». (fr)
- A seismic hazard is the probability that an earthquake will occur in a given geographic area, within a given window of time, and with ground motion intensity exceeding a given threshold. With a hazard thus estimated, risk can be assessed and included in such areas as building codes for standard buildings, designing larger buildings and infrastructure projects, land use planning and determining insurance rates. The seismic hazard studies also may generate two standard measures of anticipated ground motion, both confusingly abbreviated MCE; the simpler probabilistic Maximum Considered Earthquake (or Event ), used in standard building codes, and the more detailed and deterministic Maximum Credible Earthquake incorporated in the design of larger buildings and civil infrastructure like dams or (en)
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