arthquake is one natural phenomenon familiar to all. There Ewould hardly be any person who would not have experienced Sudden rapid tremors of ground caused by the release of energy stored in rocks, earthquakes can be both mild and severe and generally last between 50 seconds to 2 minutes. When severe, earthquakes are known to
cause a lot of damage to living and
non-living things.The severity of an earthquake is mainly determined by the Richter Scale that assigns a magnitude number to quantify the energy released by an earthquake. Apart from it. the other devices to
measure the magnitude of the earthquake are the Moment Magnitude Scale and the Mercalli Scale. If the earthquake measures 7 or more on the Richter Scale, then it is known to cause more damage, while if it measures 5 or less points it may not cause much damage. The place or location of quake origin is called the epicentre.
Most earthquakes are causally related to compressional or tensional stresses built up at the margins of the huge moving tectonic plates that make up Earth’s surface. The immediate cause of earthquake is the sudden release of stress fault or fracture in the earth’s crust. resulting in movement of the opposite blocks of rocks past one
another.
These movements cause vibrations to pass through and around the
Earth in wave form, just as ripples are generated when pebbles are
dropped in water. Volcanic eruptions, rockfalls, landslides and explosions can also cause a quake, but most of these are only of local extent. Shockwaves from a powerful earthquake can trigger smaller earthquakes in distant locations hundreds of miles away. These shock waves are also called seismic waves.
In India, the entire Himalayan region, the Deccan Plateau including Gujarat and Maharashtra, Delhi region including Haridwar, Rohtak, Sonipat and Gurgaon are seismically active.
The effect of a moderate earthquake in a congested city like Delhi with its high rise buildings and ancient structures can be very well imagined. Some of the most disastrous earthquakes to have hit the country are the Kutch quake of 2001 and Kashmir quake of 2005. With measures of 7.9 and 5.2 respectively, these both caused untold havoc in the two states. There was immense destruction, buildings collapsed, people died and dead bodies were found buried in the heaps of collapsed structures. Both were immensely tragic events in the country.
There are some precautionary steps that one can follow in an earthquake like coming outside the building at once. And if, one is on a very high floor and cannot immediately come out, then it is advisable to stand behind a door or hide beneath a sofa, bed, etc. Also one must avoid using lifts during that time. Experts also stress on having strongly built and low-rise structures.
Though earthquakes are a natural calamity that cannot be prevented, some geologists say that their intensity and frequency can be reduced if man stops tampering with Earth like digging too deep or creating or razing structures frequently. However, there is still no proven reason to believe that and the best preventive measure is preparedness to deal with it.
