UPSC Prelims 2006 · General Studies
Question 87: Geography
Consider the following statements :
- 1.The Richter scale is a logarithmic scale and so an increase of 1 magnitude unit represents a factor of 10 times in amplitude.
- 2.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?
AnswerThe answer is (a).
The Richter scale is logarithmic: each whole-number increase means a tenfold increase in the amplitude of the recorded seismic waves, so statement 1 is correct. But the energy released rises by about 32 times (roughly 31.6) per unit, not 100 times, so statement 2 is wrong. A magnitude 7 quake is therefore ten times larger in amplitude than a magnitude 6, and about 32 times stronger in energy.
- 1. Each step is a tenfold increase in wave amplitude.
- 2. Energy rises about 32 times per step, not 100.
How you could have got this
- If you were sure statement 1 is correct, (b) and (d) go: each of them leaves 1 out.
What you needed to know: Each step is a tenfold increase in wave amplitude.
- Then, if you were sure statement 2 is not correct, (c) goes: it includes 2.
What you needed to know: Energy rises about 32 times per step, not 100.
Only (a) is left. This one needs every statement.
This follows an unofficial answer: UPSC has not published its key for this year, and if that answer is wrong, so is this path.
Which options go is worked out from UPSC’s key and the options, not by a model.
Why each option is right or wrong
- (a) Correct: only statement 1 holds.
- (b) Statement 2 is false: energy rises about 32 times per unit.
- (c) Statement 2 is false.
- (d) Statement 1 is true.
Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2006, General Studies. UPSC's own paper isn't online; the words are from a published compilation. The paper on upsc.gov.in.