Question

The magnitude, M, of an earthquake is defined to be M = log StartFraction I Over S EndFraction, where I is the intensity of the earthquake (measured by the amplitude of the seismograph wave) and S is the intensity of a “standard” earthquake, which is barely detectable. What is the magnitude of an earthquake that is 1,000 times more intense than a standard earthquake? Use a calculator. Round your answer to the nearest tenth.
2
3
4.5
6.9

Answer 1

M = log(I/S) = log(1000) = 3.0, so the magnitude is 3 (to the nearest tenth).