The Richter Magnitude Scale is a method of assigning a single number to quantify the energy released during an earthquake. The magnitude is defined as the logarithm of the ratio of the amplitude of the wave's measures through a seismograph, to an arbitrary small amplitude. Therefore, an earthquake that measures 5.0 of the Richter scale has a shaking amplitude of 10 times that of an earthquake measuring 4.0. Since the middle of the 20th century, the Richter Scale has been mostly superseded by the Moment Magnitude Scale, the Richter Scale is still used in Russia and some other former Soviet Union states.