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Q59 (IAS/2001) Geography › World Physical Geography › Seismology and volcanism Answer Verified

Consider the following statements regarding the earthquakes : I. The intensity of earthquake is measured on 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 hundredfold increase in the amount of energy released. Which of these statements are correct ?

Result
Your answer: —  Â·  Correct: A
Explanation

Statements I, II and III are correct. The Mercalli (Modified Mercalli) scale measures earthquake intensity by observed effects and damage at locations, i.e., intensity, not energy [1]. Magnitude denotes the size of an earthquake as a measure of energy released and is given as a numeric magnitude (Richter/moment magnitude) [2]. Magnitudes such as the Richter (local) magnitude are based on direct instrumental measurements of seismic-wave amplitudes recorded by seismographs [2]. Statement IV is incorrect: a one-unit increase on the Richter-type scales corresponds to a tenfold increase in measured amplitude but about a 32-fold increase in energy released, not a hundredfold change [3].

Sources

  1. [1] FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.) > Chapter 3: Interior of the Earth > Measuring Earthquakes > p. 21
  2. [2] Environment and Ecology, Majid Hussain (Access publishing 3rd ed.) > Chapter 8: Natural Hazards and Disaster Management > Magnitude of Earthquake > p. 16
  3. [3] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 14: Earthquakes > 14.5. Richter Magnitude Scale > p. 182
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SIMILAR QUESTIONS

CDS-II · 2025 · Q91 Relevance score: 4.04

Which of the following statements with reference to Richter scale is/are correct ? 1. It is the intensity scale of an earthquake. 2. Richter indicates the amount of energy released during the earthquake. Select the answer using the code given below :

CDS-II · 2016 · Q14 Relevance score: 3.05

With reference to earthquakes, which of the following statements are correct? 1. Earthquakes largely occur along the converging plate boundaries. 2. Point of origin of earthquake in lithosphere is known as focus/ hypocentre. 3. Intensity of earthquake decreases with distance from the epicentre. 4. Epicentre of earthquake always remains over continents only. Select the correct answer using the code given below.

IAS · 2006 · Q22 Relevance score: 2.84

Consider the following statements: I. The Richter Scale is a logarithmic scale and so an increase of one magnitude unit represents a factor of 10 times in amplitude. II. Each integer reading of the Richter scale has an energy 100 times that of the previous integer reading. Which of the statements given above is/are correct?

CDS-I · 2025 · Q1 Relevance score: 2.40

Consider the following statements with reference to Secondary waves (S-Waves) generated during an earthquake : 1. They create troughs and crests in the material through which they pass. 2. The direction of vibrations of S-waves is perpendicular to the wave direction in the vertical plane. Which of the statements given above is/are correct ?

IAS · 2006 · Q103 Relevance score: 1.78

Each of the six faces of a cube is numbered by one of the six digits from 1 to 6. This cube is shown in its four different positions in the figures I, II, III and IV: Consider the following statements: I. Figures II and III are sufficient to know as to which face is opposite to the face numbered 6. II. Figure II and III are sufficient to know as to which face is opposite to the face numbered 4. III. Figures I and IV are sufficient to know as to which face is opposite to the face numbered 3. Which of the statements given are correct?