In seismic regions, earthquakes occur frequently and cause loss of life and property. This emphasizes the need for reliable methods of earthquake production. To predict earthquakes it is necessary to detect the fault lines where strains are building up. The following methods are used to locate areas under stains.
- In Japan, people have concentrated their study on fore-shocks that precede the main earthquake. It is hoped that this study will lead to some pattern, which can be used to predict earthquakes.
- Before an earthquake, the ground on either side of a fault suffers elastic deformation, which can be measured by triangulation with a theodolite or laser beam.
- In California (USA), uplift or subsidence of the land and changes in movement along a fault zone from a slow creep to a locked position have preceded main earthquakes. Hence it is hoped that the prediction of earthquakes may be done by monitoring ground tilt, fault movement, and seismic activity.
- Now, artificial satellites gather information from instruments, placed in the vicinity of major faults. With the help of this information, it is now possible to detect very small movements of the earth’s surface and locate areas where strain is building up.
- Recently a method has been discovered where the amount of water that a rock contains is measured. Under stains, the pores in the rock enlarge, which allows more water to enter into it. Thus, the knowledge of the water level in wells in the earthquake-affected areas is very useful in detecting rocks under stains.
In 1975 an earthquake in northeast China was predicted only hours before it occurred. As a result, thousands of lives were saved.
Controle of Earthquake:
In an earthquake-prone area, if it is known that the stain is accumulating, the threat of earthquakes can be reduced by the following methods.
- Several deep holes are drilled along a fault line in which stress has been detected. Then water is pumped down into the holes. This water acts as a lubricant, so the faulted rocks slip smoothly in a series of small nondestructive earthquakes.
- Nuclear devices may be exploded along a fault plane, which relieves stain by producing small earthquakes.