Table 4: Region falling in various zones of the country

1.6. Effects of Earthquakes

The direct and indirect effects of an earthquake includes:

1. Deformed Ground Surface: The earthquake tremors and the resultant vibrations, result in the deformation of the ground surface, due to the rise and subsidence of the ground surface and faulting activity. The alluvium filled areas of the flood plains may get fractured at several places.

2. Damage to man-made structures: Man-made structures such as buildings, roads, rails, factories, dams, bridges, etc., get severely damaged.

3. Damage to towns and cities: The towns and cities are the worst affected due to a high density of buildings and population. Under the impact of tremors, large buildings collapse and men and women get buried under the debris. Ground water pipes are damaged and thus water supply is totally disrupted.

4. Loss of human and animal life: The destructive power of an earthquake depends upon the loss it can cause in terms of loss of life arid property. The Bhuj earthquake of India in 2001 (8.1 on the Richter Scale) caused over one lakh human casualties.

5. Devastating fires: The strong vibrations caused by an earthquake can cause fire in houses, mines and factories due to the bursting of gas cylinders, contact with live electric wires, churning of blast furnaces, displacement of other electric and fire related appliances.

6. Landslides: The tremors in hilly and mountainous areas can cause instability of unconsolidated rock materials. This ultimately leads to landslides, which damage settlements and transport systems.

7. Flash floods: Very strong seismic events result in the collapse of dams and cause severe flash floods. Floods are also caused when the debris produced by tremors blocks the flow of water in the rivers. Sometimes the main course of the river is changed due to the blockage.

8. Tsunamis: When the seismic waves travel through sea water, high sea waves are generated, which can cause great loss to life and property, especially in the coastal areas.