Problem 43E

The geologist C. F. Richter defined the magnitude of an earthquake to be log10(I/S), where I is the intensity of the quake measured by the amplitude of a seismograph 100 km from the epicenter and S is the intensity of a standard earthquake where the amplitude is only 1 micron =104 cm. The 1989 Loma Prieta earthquake that shook San Francisco had a magnitude of 7.1 on the Richter scale. The 1906 San Francisco earthquake was 16 times as intense. What was its magnitude on the Richter scale?

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