Consider the following statements regarding the earthquakes:

1. The intensity of earthquake is measured on Mercalli scale.
2. The magnitude of an earthquake is a measure of energy released.
3. Earthquake magnitudes are based on direct measurements of the amplitude of seismic waves.
4. In the Richter scale, each whole number demonstrates a hundredfold increase in the amount of energy released.

Which of these statements are correct?

1. I, II and III
2. II, III and IV
3. I and IV
4. I and III

Explanation

Option (a) is correct

• The intensity of an earthquake is measured on the Modified Mercalli Intensity Scale, making Statement I correct. The magnitude of an earthquake represents the amount of energy released at the source, so Statement II is also correct. Earthquake magnitudes are determined from the amplitude of seismic waves recorded by seismographs, making Statement III correct. However, Statement IV is incorrect because on the Richter scale, each whole-number increase represents a tenfold increase in wave amplitude and roughly 31.6 times more energy released, not a hundredfold increase in energy.

Answer: (a) I, II and III