EarthQuakes
Earthquakes Suddenly shaking and trembling of Ground/ Earth surface is known as Earthquakes. The numerous shocks which continually take place are due to sharp movements along fractures (called faults) which relieve stress in the crustal rocks. Stress accumulates locally from various causes until it exceeds the strength of the rocks, when failure and slip along fractures occur, followed usually by a smaller rebound. A small movement on a fault, perhaps a few centimeters or less, can produce a considerable shock because of the amount of energy involved and the fault may 'grow' by successive movements of this kind. Earthquakes range from slight tremors which do little damage, to severe shocks which can open fissures in the ground, initiate fault scarps and landslides, break and overthrow buildings, and sever supply mains and lines of transport. The worst effects are produced in weak ground, especially young deposits of sand,...