To find the energy of Earthquakes (measured in Joules) scientists use the equation: E = (2.5 x 104) x 101.5M where M is the magnitude of the earthquake. The 1989 San Francisco earthquake, which killed 90 people, had a magnitude of 7.1. Compare the energy of that earthquake with the 2003 earthquake that destroyed the ancient city of Bam, Iran, which had magnitude 6.3 and killed an estimated 50,000 people.