Along with war and pestilence, earthquakes rank as one of the worst killers in the world. They have unique characteristics of striking without warning both in time and space.
The surface of the earth sits on several gigantic tectonic plates that move by a few centimeters each year. These plates usually move against each other resulting in faults which become quite vulnerable. These stresses or faults break causing earthquakes.
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Earthquakes are proportional to the density of quakes. The timing of the earthquake also plays an important role in the amount of destruction it manages to cause.
The Indian sub-continent has a history of major earthquakes. In fact, geographical statistics show that at least 54 percent of India’s land is vulnerable to earthquakes. The Indian regions are divided into four seismic zones, 2,3,4 and 5. 2 being the lowest and 5 being the highest.
Coming to the types of earthquakes, there are five kinds depending upon their magnitude rated from 1 up to 9 on the Richter scale.
The first one being the micro earthquake which have their magnitude lesser than 2 on the Richter scale. These quakes are hardly felt, and the frequency is also quite large. Thus, they have no damaging effect.
The second one is a slight earthquake whose magnitude goes up to 4.9 wherein you can feel the quake, but the area gets limited and the extent of the feel reduces. It only affects very weak structures, causing slight crack or something like that.
The third one is a moderate earthquake whose magnitude ranges between 5 and 6.9. These quakes not only affect the regions in proximity of the centre of the earthquake and goes up to 100s of km.
The fourth one if a great earthquake which ranges between 7 and 7.9 in magnitude. These have the potential of causing massive damage to both life and property.
The fifth one if very great wherein the magnitude is 8 or more on Richter scale. These quakes are deadly in nature and can cause a catastrophe destroying several settlements at once and the repercussions are felt for years. In fact, anything beyond 9 is a tectonic destruction.
The higher the magnitude of the earthquake, the longer is the return period of the quake. For instance, the return period of quakes of magnitudes 8 or more is beyond 50 years.
An example of a very great earthquake is the Shillong Earthquake which occurred in the year 1897. The epicenter was in the southern margin of the Shillong Plateau on the Dauli fault. This quake, in less than a minute, managed to cause massive destruction in Shillong and its adjoining areas. Because of the quake, over 30 lakhs fishers and waterfalls were formed while rivers changed their course.
Usually, after any earthquake, sometimes there are aftershocks. There are rare occasions when foreshocks also occur. However, a foreshock is no indication of an upcoming earthquake.
Every time an earthquake increases by one magnitude, the exponential increase in energy is by 10 times. Earthquakes occur in various depths which means that the place of origin could be deep inside. The point first above the origin on the surface of the earth is the epicenter. The larger the magnitude of the earthquake, the more is the depth and the more is the devastation.
There has been a hoax circulating regarding a major earthquake likely to strike Delhi and the NCR region between April 7 and 15. This kind of prediction is a complete hoax as there is no technology that exists for earthquake predictions.
Scientists have tried several ways of predicting an earthquake and tsunami, but none have been successful until now. The unanswered questions associated with earthquakes of where, when, how and why, still remain a mystery.
Please Note: Any information picked from here must be attributed to skymetweather.com
