Q. Each increase of one unit on the Richter  scale represents a ___fold increase in the magnitude of an earthquake?
Answer: 10
Notes: The Richter magnitude of an earthquake is determined from the logarithm of the amplitude of waves recorded by seismographs. Because of the logarithmic basis of the scale, each increase of one unit on the scale represents a 10-fold increase in the magnitude of an earthquake. Two points on the Richter scale e.g., from 4 to 6 or from 5 to 7, corresponds to about 1000 times the energy release.