Earthquake 


Q1. Consider the following statements: I.A.S. (Pre) 2006

  1. The Richter scale is a logarithmic scale and so an increase of 1 magnitude unit represents a factor of 10 in amplitude.
  2. Each integer reading of the Richter scale has an energy 100 times that the previous integer reading.

Which of the statement(s) given above is/are correct?

(a) 1 only

(b) 2 only

(c) Both 1 and 2

(d) Neither 1 nor 2

Ans. (a)

Explanation:

  1. Earthquake magnitude is measured by the Richter scale, while intensity is measured by the Mercalli scale.
  2. The Richter magnitude scale was developed in 1935 by seismologist Charles Francis Richter of the California Institute of Technology.
  3. The Richter scale is logarithmic with base 10; hence, an increase of one magnitude represents 10 times greater wave amplitude. Hence, statement (1) is correct.
  4. Each whole number increase on the Richter scale represents about 32 times more energy release, not 100 times; hence, statement (2) is incorrect.

Q2. Consider the following statement about earthquake – I.A.S. (Pre) 2001

  1. Intensity of earthquake is measured on Mercalli Scale.
  2. Earthquake’s magnitude is the measurement of energy released.
  3. Magnitude of earthquake depends directly upon Amplitude of an earthquake waves.
  4. Every integer on Richter Scale shows a 100 times increase in energy released.

Which of the statements are true?

(a) 1, 2 and 3

(b) 2, 3 and 4

(c) 1 and 4

(d) 1 and 3

Ans. (a)

Explanation:

  1. The intensity of an earthquake is measured by the Mercalli scale; hence, statement (1) is correct.
  2. The magnitude of an earthquake represents the energy released during an earthquake; hence, statement (2) is correct.
  3. The magnitude of an earthquake depends on the amplitude of seismic waves, as measured by the Richter scale; hence, statement (3) is correct.
  4. Each integer increase on the Richter scale indicates about 32 times more energy release, not 100 times; hence, statement (4) is incorrect.

Q3. Which of the following instruments is used to record seismic waves? U.P. P.C.S. (Mains) 2017

(a) Seismogram

(b) Seismograph

(c) Seismoscope

(d) Seismometer

Ans. (b)

Explanation:

  1. A seismograph is an instrument used to detect and record earthquakes; hence, option (b) is correct.
  2. The seismometer is the internal component of a seismograph, which may consist of a pendulum or a weight fixed on a spring.
  3. A seismogram is the recorded representation of an earthquake at a particular location by a seismograph.
  4. Thus, a seismograph generally refers to the seismometer along with its recording device as a complete unit.

Q4. Which one of the following statements about the 2004 Indian Ocean earthquake and the resulting Tsunami is not correct? 47th B.P.S.C. (Pre) 2005

(a) The earthquake originated due to slipping of about 1,200 km of fault line by 15 m along the subduction zone where the India Plate subducts the Burma plate at the Sunda Trench.

(b) The resulting tsunami devastated the shores ranging from the coast of Indonesia to the east coast of Africa, some 8,500 km away from the epicenter.

(c) As per the current estimates, the quake-generated tsunami killed more than 50 lakh people, in addition to unaccounted dead bodies swept out to sea.

(d) Bangladesh had very few casualties because the quake-affected fault line was in a nearly north-south orientation, the greatest strength of the tsunami waves was in an east-west direction.

Ans. (c)

Explanation:

  1. The Indian Ocean earthquake occurred on 26 December, 2004 due to the movement along the boundary of the India and Burma tectonic plates near the western coast of Sumatra Island, Indonesia.
  2. An estimated 1,300 km of fault line slipped by about 15 m, making statement (a) almost correct.
  3. The tsunami affected coastal areas from Indonesia, Sri Lanka and India up to Somalia on the east coast of Africa; hence, statement (b) is nearly correct.
  4. Around 2–3 lakh people lost their lives due to the disaster, not more than 50 lakh; hence, statement (c) is incorrect. 
  5. Bangladesh experienced very few casualties due to the orientation of the fault line and direction of tsunami wave energy; hence, statement (d) is correct.

Q5. Cocos Plate lies between- 63rd B.P.S.C. (Pre) 2017

(a) Central America and Pacific Plate

(b) South America and Pacific Plate

(c) Red Sea and Persian Gulf

(d) Asiatic Plate and Pacific Plate

(e) None of the above/More than one of the above

Ans. (a)

Explanation:

  1. The Cocos Plate is an oceanic tectonic plate located in the eastern Pacific Ocean.
  2. It lies between Central America and the Pacific Plate; hence, option (a) is correct.