The point inside the earth where an earthquake originates is known as the

The correct answer is C, Focus. The focus, also called the hypocentre, is the point below the surface at which the strained rock ruptures and releases its stored elastic energy as seismic waves. Its depth decides how widely the shock is felt: shallow-focus earthquakes are more damaging near the source than deep-focus ones of the same magnitude.

Option A, the epicentre, is the point on the ground surface lying vertically above the focus, so it is a surface point and not the place of origin. Option B, a fault line, is the fracture in the crust along which the blocks move; the focus lies on a fault but the fault itself is a line or plane, not a point. Option D, the shadow zone, is the belt on the far side of the earth, between about 103 and 142 degrees, which receives no direct P or S waves. The pair focus and epicentre is the most frequently asked distinction in this chapter.