Narad's beneficial role The moral fibre, personality the character of sage Narada has to be fully grasped against the negative standing that is latent in the term 'kalaha Priya' attributed to him, pointed out Sri k.Srinivasam in a courage. This point is explain in detail by Vyas in the Devi Bhagwat Puran as an answer to the issue that janamejaya rises with reference to kama's as killing of 6 infants who were born to Devaki. It is said that Kansas decided to spare the 1st new born infants of Devaki knowing that only the eighth child was a real threat . But Narad intervences and changes his decision. So JanameJaya wonder how Narad, adeva Rishi, age of Great reputation, and Janani, can prompt kamsa thus . How did the sage, the embodiment of Dharma, stop down to a bit the killing of infants? Is this not considered as a serious crime that deserve the most grave punishment? Vyas explain that Northern character should be understood in prop...
What is at the heart of earthquake? Can they be predicted? Is it possible to set up early warning systems?
The story so far: recently a powerful earthquake off magnitude 5.9 on the Richter scales struck a remote town in Afghanistan, killing over thousands and injuring many more. According to the U.S. federal emergency management agency, have 5.9 on the Richter scale is roughly equally 37x energy released by the atomic bomb dropped on Hiroshima. Experts are still trying to figure out the best early warning system to mitigate the damage caused by earthquakes.
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How do earthquakes happen?
- According to the theory of plates tectonics , the Earth's crust and upper mantle are made of rigid plates that can move relative to one another.slip on fault near the plate boundary results in earthquake. The points inside the earth where the earthquake rupture starts is called the focus or hypocentre . The point directly above it on the surface of the earth is the epicenter.
- Any elastic material when subjected to stress , stretches reaches in a proportion way , until the elastic limit is crossed,it breaks. Similarly, the earth also has an elastic limit and when the strech is higher than it's limit,it breaks. Then there is generation of heat , and energy is released. Since the material is elastic,the energy is released in the form of elastic waves. These propagates to a distance determined by the extent of impact.These are known as seismic waves.
- Earthquakes are measured by seismographic network, which are made of seismic stations , each of which measures measures the shaking of the ground beneath it . In India,the National Seismological Network does this work. It has a history of about 120 years and it's sensere can now detect an earthquake within 5 -10 minutes. According to the Shyam S Rai who is Raja Ramanna fellow and professor Emeritus at the Indian institute of science education and research Pune, the wave parameters are measured, not the total energy released. He explains that there is a relationship between the quantum of energy released and the wave amplitude. The amplitude of the wave is a function of the time period of the wave. It is possible to convert the measured wave into the energy released for the earthquake. This is what seismologist call the magnitude of the Earthquake.
- This is the measure of the magnitude of the earthquake and was first defined by Charles F.Richter of the Callifornia Institute of Technology,U.S.,in 1935.The magnitude of the earthquake is logarithm of the amplitude of the wave measured by the seismographs . Richter scale magnitude are expressed as a whole whole number and a decimal part,for example 6.3 or 5.2 . Since it is logarithemic scale,an increased of the whole number by one unit signifies a tendfold increased in the amplitude of the wave and a 31 time increased of the energy released.
- Based on seismicity intensity of Earthquake experienced,and geological and tectonic qualities of a region, countries are divided into several zones .In India,for example, there are four zones , designated zone II-zone V. Among these, zone V is the most hazardous and zone II the least hazardous.
- Since parameters of the Earthquake are unknown,it is near impossible to predict an earthquake. The problem with earthquake is that they are heavily dependent on the material property , which varies from place to place,says professor Rai. If there are elastic waves propagating through a material there are two kind of waves -the primary wave which reached first, and the second wave called the secondary wave , which is more distructive . Suppose the primary wave is measured,and we have efficient computer system, all the inputs are excellent data collection,then it can be said that a possible earthquake of this much and magnitude of energy has occured and this could lead to ground amplitude which could be distructive . If it is known that the amount of energy released is extremely high, trains and power grids can be shut down and the damage minimised. "This has worked in some locations, but not on a large commercial basis ,"says prof.Rai ." The most successful early warning system in Japan . They have several hundreds of thousands recording devices . Responses are sent to a central point where they estimate wheather it is large enough to form a Tsunami or some other hazard ,and precautionary steps are taken ,"he points out .
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