Point of Origin of Earthquake Wave is known as
- (a)Epicentre
- (b)Focus
- (c)Photosphere
- (d)Seismic Zone
Correct — B, Focus. The focus (also called the hypocentre) is the point inside the Earth where an earthquake actually originates — where the rock ruptures and seismic waves begin to radiate outward in all directions. The point on the ground surface directly above the focus is the epicentre, but the origin of the waves is the focus.
- (a)Epicentre — The epicentre is the point on the Earth's surface directly above the focus — where shaking is usually strongest — but it is not where the waves originate.
- (c)Photosphere — The photosphere is the visible surface layer of the Sun; it has nothing to do with earthquakes.
- (d)Seismic Zone — A seismic zone is a region prone to earthquakes, not a single point of origin.
An earthquake is the release of stored strain energy along a fault. The rupture starts at the focus (hypocentre) below the surface, sending out seismic waves — primary (P) and secondary (S) body waves through the interior and surface (L) waves along the ground. The epicentre is the surface point vertically above the focus.
The key is distinguishing 'point of origin' (focus, inside the Earth) from the 'surface point above it' (epicentre). Photosphere and seismic zone are placed as odd terms — one solar, one a region.
- The focus (hypocentre) is the underground point where an earthquake originates.
- The epicentre is the surface point directly above the focus.
- Seismic waves radiate outward from the focus as P, S and surface waves.
- Focus depth is classed as shallow, intermediate or deep.
Waves start at the focus below ground; the epicentre is only the surface point above it.
- Swapping focus and epicentre — the epicentre is only the surface point.
- Being misled by 'photosphere', a solar term slipped into a geography item.
Asked as a direct definition or by pairing focus/epicentre in statement-based questions.
Consider the following statements regarding earthquakes: I. The intensity of an earthquake is measured on the Mercalli scale. II. The magnitude of an earthquake is a measure of energy released. III. Earthquake magnitude is measured from seismic-wave amplitude...
- (a) I, II and III
- (b) II, III and IV
- (c) I and IV
- (d) I and III
Answer(a) I, II and III
Same concept — earthquake fundamentals: how the shock originates and how it is measured (intensity vs magnitude).
Which of the following statements regarding earthquakes is/are correct? 1. The point on the Earth’s surface directly above the focus is called the epicentre of the earthquake. 2. Earthquakes generate Primary and Secondary waves that radiate outward from the earthquake focus. 3. Deep-focus earthquakes are likely to cause more damage than shallow-focus earthquakes. Select the answer using the code given below:
- (a) 1 only
- (b) 1 and 2 only
- (c) 2 and 3 only
- (d) 1, 2 and 3
Answer(b) 1 and 2 only
Same concept — focus vs epicentre and the radiation of seismic waves from the focus.
- practice — not a real PYQ
The point on the Earth's surface directly above the focus of an earthquake is called the
- (a)Epicentre
- (b)Hypocentre
- (c)Seismic zone
- (d)Fault line
Answer(a) Epicentre — vertically above the focus.
- practice — not a real PYQ
Which seismic waves cannot travel through liquids?
- (a)P-waves
- (b)S-waves
- (c)Surface waves
- (d)All of these
Answer(b) S-waves — secondary (transverse) waves are blocked by liquids.