Earthquake and its causes

An earthquake is a series of vibrations on the earth's surface caused by the generation of elastic (seismic) waves due to sudden rupture within the earth during release of accumulated strain energy.

Faulting may be considered as an immediate cause of an earthquake. Due to constant movement of plates, deformation is caused which results to generations of strain energy.

Indian plate is moving in north-north-east direction and colliding with Eurasian plate along the Himalayas.

DEFINITIONS

EPICENTRE: It is the point on the (free) surface of the earth vertically above the origin place (hypocentre) of an earthquake. This point is expressed by geographical latitude and longitude.

MAGNITUDE : It is a quantity to measure the size of an earthquake in terms of its energy and is independent of the place of observation.

RICHTER SCALE : Magnitude is measured on the basis of ground motion recorded by an instrument and applying standard correction for the epicentral distance from recording station. It is related with the logarithm of amount of energy released by an earthquake and expressed in Richter Scale.

INTENSITY: It is the rating of the effect of an earthquake at a particular place, based on the observations of the damaged areas, using a descriptive scale like Modified Mercalli Scale.

CLASSIFICATION OF EARTHQUAKES

Slight : Magnitude up to 4.9 on the Richter scale

Moderate : Magnitude 5.0 to 6.9

Great : Magnitude 7.0 to 7.9

Very great : Magnitude 8.0 and more

EARTHQUAKE MONITORING

India Meteorological Department (IMD) is the national agency for detecting and locating earthquakes and evaluation of seismicity in different parts of the country.

EARTHQUAKE PREDICTION

Earthquake prediction is not yet scientifically possible with reasonable accuracy in terms of location, time and magnitude.

DO's

Take shelter under a desk, table, bed or doorway during an earthquake.

Provide help to others and develop confidence.

Shut off kitchen gas.

Keep stock of drinking water, food stuff and first aid arrangements.

If you are in a moving vehicle, stop and stay in vehicle.

Follow and advocate local safety building code for earthquake resistant construction.

Heavy objects, glasses should be kept on lower shelf.

Turn on transistor or T.V. to get latest information.

Make plan and preparation for emergency relief.

DON'Ts

Do not get panicky

Do not use candles, matches etc and do not switch o any electric mains immediately after an earthquake.

Do not spread and believe in rumours

Do not run through or near buildings during an earthquake