An earthquake is the shaking or trembling of the earth’s surface, caused by the sudden movement of a part of the earth’s crust. They result from the sudden release of energy in the Earth’s crust that creates seismic waves or earthquake waves.
Causes of the earthquake are as follows:
Sudden slipping of rock formations along faults and fractures in the earth’s crust happen due to constant change in volume and density of rocks due to intense temperature and pressure in the earth’s interior.
Volcanic activity also can cause an earthquake but the earthquakes of volcanic origin are generally less severe and more limited in extent than those caused by fracturing of the earth’s crust.
Earthquakes occur most often along geologic faults, narrow zones where rock masses move in relation to one another. The major fault lines of the world are located at the fringes of the huge tectonic plates that make up Earth’s crust.
Plate tectonics: Slipping of land along the fault line along, convergent, divergent and transform boundaries cause earthquakes. Example: San Andreas Fault is a transform fault where Pacific plate and North American plate move horizontally relative to each other causing earthquakes along the fault lines.
Most earthquakes are causally related to compressional or tensional stresses built up at the margins of the huge moving lithospheric plates The immediate cause of most shallow earthquakes is the sudden release of stress along a fault, or fracture in the earth’s crust.