Forecasting a probable location, magnitude and other important features of forthcoming seismic event is called Earthquake prediction. In the effort to predict earthquakes, people have tried to associate an impending earthquake with such varied phenomena as seismicity patterns, electromagnetic fields (seismo-electromagnetics), ground movement, weather conditions and unusual clouds, radon or hydrogen gas content of soil or ground water, water level in wells, animal behavior, and the phases of the moon. Many pseudoscientific theories and predictions are made, which scientific practitioners find problematic. The natural randomness of earthquakes and frequent activity in certain areas can be used to make "predictions" which may generate unwarranted credibility.
Long Term Forecast
The study of regional seismicity and the outline of seismic zones make it possible, within the framework of Plate Tectonics, to forecast the regions in which earthquakes will occur. Earthquake catalogs of a region, or the magnitude-frequency plot for the region, help on statistical basis, to anticipate (make a long-term forecast of) earthquakes. This is useful to develop strategy, which reduce human and material losses.
Short-term Prediction
Short-term prediction implies the ability to specify in advance the exact place, date (as precisely as possible) and magnitude of a future earthquake. Despite extensive research in advanced countries, the system of earthquake prediction has not attained the level to use confidently outside experimental environments. Many questions on the cost-effectiveness of prediction, especially in developing countries, have been raised. The money could be better spent on reducing vulnerability of existing structures.
There is no any discovery for the prediction of occurrence of earthquake to find when and where it happens.
The study of regional seismicity and the outline of seismic zones make it possible, within the framework of Plate Tectonics, to forecast the regions in which earthquakes will occur. Earthquake catalogs of a region, or the magnitude-frequency plot for the region, help on statistical basis, to anticipate (make a long-term forecast of) earthquakes. This is useful to develop strategy, which reduce human and material losses.
Short-term Prediction
Short-term prediction implies the ability to specify in advance the exact place, date (as precisely as possible) and magnitude of a future earthquake. Despite extensive research in advanced countries, the system of earthquake prediction has not attained the level to use confidently outside experimental environments. Many questions on the cost-effectiveness of prediction, especially in developing countries, have been raised. The money could be better spent on reducing vulnerability of existing structures.
SEISMIC HAZARDS
Earthquake has two types of hazards: primary and secondary hazards. The primary hazard resulting from an earthquake is the ground movement and shaking. Surface seismic waves cause most severe hazards to human viz.:
• Building collapse - Damage to buildings and other structures will differ according to the surface materials they are built on. Solid bed rock is more stable than unconsolidated sediments which can amplify the shaking.
• Underground pipes and power lines may be severed by ground motion resulting in fires and explosions
• Ruptured water pipes mean no water to extinguish fires. Secondary hazards are soil liquefaction, landslides, avalanches and tsunamis.
Soil Liquefaction: Liquefaction is a condition when a solid material turns into a liquefied state due to an increase in water pressures of the pore as a result of groundshaking during an earthquake and the strength and stiffness of a soil is reduced. It occurs in saturated soils, that is, soils in which the space between individual particles is completely filled with water. This water exerts a pressure on the soil particles that influences how tightly the particles themselves are pressed together. Prior to an earthquake, the water pressure is relatively low. However, earthquake shaking can cause the water pressure to increase to the point where the soil particles can readily move with respect to each other. Structures such as bridges, dams and subsurface pipes will be damaged apart from structures standing on such soil base. Liquefaction and related phenomena have been responsible for tremendous amounts of damage in historical earthquakes around the world.
Earthquake has two types of hazards: primary and secondary hazards. The primary hazard resulting from an earthquake is the ground movement and shaking. Surface seismic waves cause most severe hazards to human viz.:
• Building collapse - Damage to buildings and other structures will differ according to the surface materials they are built on. Solid bed rock is more stable than unconsolidated sediments which can amplify the shaking.
• Underground pipes and power lines may be severed by ground motion resulting in fires and explosions
• Ruptured water pipes mean no water to extinguish fires. Secondary hazards are soil liquefaction, landslides, avalanches and tsunamis.
Soil Liquefaction: Liquefaction is a condition when a solid material turns into a liquefied state due to an increase in water pressures of the pore as a result of groundshaking during an earthquake and the strength and stiffness of a soil is reduced. It occurs in saturated soils, that is, soils in which the space between individual particles is completely filled with water. This water exerts a pressure on the soil particles that influences how tightly the particles themselves are pressed together. Prior to an earthquake, the water pressure is relatively low. However, earthquake shaking can cause the water pressure to increase to the point where the soil particles can readily move with respect to each other. Structures such as bridges, dams and subsurface pipes will be damaged apart from structures standing on such soil base. Liquefaction and related phenomena have been responsible for tremendous amounts of damage in historical earthquakes around the world.
Landslides: Sudden mass movement of soil can result from the earthquakes. The stress resulting from the ground shaking of an earthquake can result in slope failure on even gentle slopes. Landslides, rock and snow avalanches can overrun people and structures, cause building collapse, break underground pipes and disrupt rescue efforts by blocking roads. In many earthquakes the land sliding has caused as much more damage than the ground shaking.
Tsunami: A Tsunami, Japanese word for harbor wave, is a series of huge waves that occur after an undersea disturbance, such as an earthquake or volcano eruption. The waves travel in all directions from the area of disturbance, much like the ripples that take place after throwing a rock. The waves may travel in the open sea as fast as 450 miles per hour. As the big waves approach shallow waters along the coast they grow to a great height and smash into the shore. They can be as high as 100 feet. They can cause a lot of destruction on the shore.
Fire: Fire is one of the most devastation events after the earthquake and it may be resulted from the principal ignition sources as overturning of electrical appliances, short-circuiting of electrical equipment, gas leakage from damaged equipment and pipe work and leakage of flammable fluids (including fuels for emergency generators etc.). Spillage of chemicals may also be a potential ignition source in buildings where they are utilized or stored.
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