Use the following information to answer the next question. earthquake intensity, i, is given by the equation lo(10) where m is the magnitude measured to the nearest tenth on the richter scale and lo is the reference intensity in 1906, the san francisco bay area had an earthquake with a magnitude of 7.8 richter scale. on the what is the magnitude of an earthquake that is 158 times less intense than the 1906 san francisco bay earthquake? a. 2.2 b. 3.5 c. 5.6 d. 6.3 4.