Causes of earthquake

Most earthquakes are usually related to compressional or tensional stresses built up at the margins of the huge moving lithospheric plates that make up the earth's surface.The immediate causes of most shallow earthquakes is the sudden release of stress along a fault or fracture in the earth's crust, resulting movements of the opposing blocks of rock past one another.These movements cause vibrations to pass through and around the earth in wave form just as ripples are generated when a pebble is dropped into water.Volcanic eruption, rock falls, landslides and explosions can also cause an earthquake but most of these are of only local extent.Shock waves from powerful earthquake can trigger a smaller earthquake in a distant location hundreds of miles away if geological conditions are favourable.