The magnitude R on the Richter scale of an earthquake of int

The magnitude, R, on the Richter scale of an earthquake of intensity I is given by R = log (I/I_0), where I_0 is the intensity of a barely felt zero-level earthquake. The Loma Prieta earthquake of 1989 in Northern California was 10^7.1 as intense as a zero-level earthquake. What was its magnitude on the Richter scale?

Solution

R = log(I/Io) ; Io = intensity of zero level earthquake ;

In northen California : I/Io = 10^7.1

R = log(10^7.1) = 7.1log10 = 7.1