Richter magnitude scale

The Richter scale was developed by American seismologist Charles F. Richter (1900-1985) to measure the intensity of earthquakes.

In the formula, R represents the Richter magnitude, I represents the intensity of the earthquake, and Io is a constant.

Due to the logarithmic nature of the formula, each increase in one unit on the Richter scale corresponds to a tenfold increase in the amount of energy released by the earthquake!

In 1976, the Tangshan earthquake in China was measured to have an intensity of 79,432,000 × Io. Can you calculate how many Richter scale units that earthquake was on?