Example

Comparing Earthquake Intensities: 1906 San Francisco vs. 1989 Loma Prieta

To compare the 1906 San Francisco earthquake (magnitude 7.8) and the 1989 Loma Prieta earthquake (magnitude 6.9), convert their magnitudes to intensities. Using the earthquake intensity model R=logIR = \log I, the equivalent exponential form is I=10RI = 10^R. The intensities are 107.810^{7.8} and 106.910^{6.9}, respectively. The ratio of the 1906 earthquake's intensity to the 1989 earthquake's intensity is 107.8106.9\frac{10^{7.8}}{10^{6.9}}. Subtracting the exponents gives 100.910^{0.9}, which evaluates to approximately 7.94. Thus, the 1906 earthquake was approximately 7.94 times as intense as the 1989 earthquake.

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Updated 2026-06-29

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