What is the magnitude of an earthquake, y, that is 10 times as intense as the previous earthquake (rounded to the nearest tenth)?
y = log 10 + 7.9 = 1 + 7.9 = 8.9
What intensity, x, is the aftershock with a magnitude of y = 8.7 (rounded to the nearest whole number) compared with the original 7.9 earthquake?
8.7 = log x + 7.9 subtract 7.9 from both sides
0.8 = log x
This says that x = 100.8 = about 6.3 = about 6 [rounded to the nearest whole number]
