Which of the following statements is/are correct ? 1. Hypocenter is the point on the surface of the Earth, nearest to the focus. 2. Velocity of earthquake waves is higher in denser materials. 3. P waves move faster and are the first to arrive at the surface of the Earth. Select the correct answer using the code given below :
- (a)1 and 2
- (b)2 and 3
- (c)1 and 3
- (d)3 only
Correct — B, 2 and 3. Statement 1 is wrong: the point on the Earth's surface directly above the focus is the epicentre, not the hypocentre — 'hypocentre' is another name for the focus itself, the underground point where the rupture starts. Statement 2 is correct: seismic waves travel faster through denser, more rigid rock, which is why their speed rises with depth. Statement 3 is correct: Primary (P) waves are the fastest seismic waves and reach a recording station first, ahead of the slower Secondary (S) waves. So statements 2 and 3 are right and 1 is wrong.
- (a)1 and 2 — Statement 1 is false — the surface point above the focus is the epicentre, not the hypocentre — so this pairing is wrong even though statement 2 is correct.
- (c)1 and 3 — Includes the false statement 1 (hypocentre is not the surface point above the focus), so it cannot be right; the correct true pair is 2 and 3.
- (d)3 only — Under-counts. Statement 2 (waves travel faster in denser material) is also true, so the answer is 2 and 3, not 3 alone.
An earthquake starts at the focus (hypocentre) below ground; the point on the surface directly above it is the epicentre. The energy travels as seismic waves whose speed increases in denser, more rigid rock. Body waves come in two kinds: fast Primary (P) waves, which arrive first, and slower Secondary (S) waves that follow.
The single trap is the focus/epicentre mix-up in statement 1 — swap the definitions and it becomes false. The two physics facts (faster in denser rock; P before S) are standard, so once you reject statement 1 the answer is 2 and 3.
- Focus (hypocentre) = the underground point where an earthquake originates; epicentre = the surface point directly above it.
- Seismic waves travel faster through denser, more rigid material, so their speed generally increases with depth.
- P (Primary) waves are the fastest and arrive first; S (Secondary) waves are slower and arrive later.
- P waves are longitudinal and can pass through solids and liquids; S waves are transverse and cannot travel through liquids.
- Calling the surface point above the focus the 'hypocentre' — it is the epicentre.
- Thinking S waves arrive first — P (Primary) waves are always first.
A statements-based earthquake question mixes a true physics fact with a swapped definition (focus/epicentre or P/S order) — check each definition carefully.
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 magnitudes are based on direct measurements of the amplitude of seismic waves. IV. In the Richter scale, each whole number demonstrates a hundred-fold increase in the amount of energy released. Which of these statements are correct?
- (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 earthquake theme — measuring magnitude from seismic-wave amplitude, closely tied to the P and S wave behaviour tested here.
Consider the following geological phenomena: 1. Development of a fault 2. Movement along a fault 3. Impact produced by a volcanic eruption 4. Folding of rocks Which of the above cause earthquakes?
- (a) 1, 2 and 3
- (b) 2 and 4
- (c) 1, 3 and 4
- (d) 1, 2, 3 and 4
Answer(a) 1, 2 and 3
Deals with what generates the seismic energy at the focus — the origin of the very waves (P and S) whose properties this question examines.
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
Directly on the focus/epicentre definition and the P and S waves radiating from the focus — the exact points that decide this question.
Point of Origin of Earthquake Wave is known as
- (a) Epicentre
- (b) Focus
- (c) Photosphere
- (d) Seismic Zone
Answer(b) Focus
Nails the term in statement 1 — the underground point where an earthquake starts is the focus (hypocentre), not the surface point (epicentre).
- practice — not a real PYQ
The point on the Earth's surface vertically above the focus of an earthquake is called the:
- (a)Hypocentre
- (b)Epicentre
- (c)Seismic zone
- (d)Fault line
Answer(b) Epicentre — the focus (hypocentre) is underground; the epicentre lies on the surface directly above it.
- practice — not a real PYQ
Which seismic waves are the first to be recorded at a seismograph station?
- (a)S waves
- (b)P waves
- (c)Surface (L) waves
- (d)They arrive together
Answer(b) P waves — Primary waves are the fastest and always arrive first.