Question

write a paragraph on earthquake in 800 words

Answer 1

According to a report a thousand quakes occur daily in the world. The intensity is measured on Richter scale developed by Charles F. Richter, an American seismologist in 1935.

Most of the earthquakes that occur daily are of a magnitude of 2R and are not hazardous. Most of the damaging ones measure more than 5. Those that cross 7 are most serious. Each (lumber on the Richter scale represents an intensity of ten times more than the previous number i.e. the intensity of a quake measuring 7 is ten times stronger than that measuring 6.

Most of the damaging earthquakes in India have been between 6 and 8.5 (Assam in 1950). Worldwide, the Mexico quake of 1985 measured 8.1, of Japan in 1933 and Colombo Equator border in Pacific Ocean in 1906 measured 8.9 the highest recorded anywhere. Richter scale has been considered a traditional system. The modified Mercalli Intensity Scale (MM) classifies earthquakes into 12 categories. The Mexico (1985) earthquake had an MM intensity of VIII to IX. It took 5,000 lives and injured 10,000.

There may be a million quakes a year. But only those that occur in surface in populous areas cause death and devastation. Most of these million are much beneath the surface of earth or the sea. The energy released by a considerably large earthquake is about 180 million metric tons of TNT i.e. near about 10,000 times more than the Hiroshima atom bomb.

There are a number of theories about the reasons of earthquakes. The most prevalent is the 'plate tectonics' theory. It says that earth's surface consists of seven large rigid plates. There are an equal number of small plates. These plates move slowly past one another.

The motion stretches or squeezes rocks at the edge of the plates. If the force is great the rocks break and shift. This causes an earthquake. These ruptures (breaks) are known as faults. Only a few of them are visible like the San Andrea Fault in California. The place where the fault occurs is known as epicenter. The energy released in an earthquake travels away in the form of waves. These are called 'seismic waves' and can be recorded in seismographic stations throughout the world if the quake is a large one. Seismic waves have three types. 'Compressional’ or longitude waves are sound waves that travel at a speed of eight kms a second. As the rocks vibrate in the direction of the movement of waves it causes the rocks to change volume. 'Shear' or transverse waves travel at half the speed of compressional waves. The rocks vibrate at right angles to the direction of the movement of waves. This results a change in the shape of rocks. The speed of 'Surface' waves is lesser than that of shear' waves. They are limited to the surface of the Earth. Seismic waves pass through the earth in 21 minutes.






NJG Negi and Krishnabrahaman of the National Geophysical Research Institute (NGRI) have a bit different view. According to them it was because of reactivation of Kurudwadi fault that they had discovered in 1973 on the basis of gravity data. The gravitational force differs from place to place and it gives clue to the faults. According to them gravity anomaly over the Bombay region 'is the highest' in India.

Earthquakes have been occurring for thousands of years. European countries have evolved methods of predicting. Vinod K Gaur, former Director of National Geophysical Research Institute complained that Indian Meteorological Department has not perfected the system of predicting earthquakes. According to him "The Indian plate, which is one of the fastest moving plates in the world, moving about five and half centimeters every year is steadily moving northward towards the Himalayas and parts of it are already bent under the great range of mountains. The plate is getting the push from the Karsberg Ridge in the Arabian sea." It might have caused the earthquake.

Answer 2

Answer:

Simply speaking, Earthquake means the shaking of the Earth’s surface. It is a sudden trembling of the surface of the Earth. Earthquakes certainly are a terrible natural disaster. Furthermore, Earthquakes can cause huge damage to life and property. Some Earthquakes are weak in nature and probably go unnoticed. In contrast, some Earthquakes are major and violent. The major Earthquakes are almost always devastating in nature. Most noteworthy, the occurrence of an Earthquake is quite unpredictable. This is what makes them so dangerous.