Invented by Charles Richter in 1935 , Richter scale is used to measure the magnitude of earth quakes. The scale, more formally known as the Richter magnitude test scale, ranges from 0 to over 8.0. It is a logarithmic scale, meaning each unit increase on the scale corresponds to an absolute increase by an order of magnitude, or factor of 10.
Earthquakes less than about 2 on the Richter scale are meaningless as they can barely even be measured, much less felt. An earthquake is not really newsworthy until it hits about 5. At magnitudes of 7.0 or 8.0 the damage can be catastrophic.
The magnitude of an earthquake is measured using a seismometer. The original Richter scale was based on a particular sort of seismometer. The device consists of a weight held in a way of measuring the displacement of the weight from the reference point due to any vibration. The earthquake’s strength is measured by the degree to which it causes the weight to be displaced. Because the seismometer is rarely at the epicenter of an earthquake, calibration techniques are used to determine what the displacement would have been if it were actually located there.
Earthquakes cannot be measured very accurately using the Richter scale when the magnitude is above about 8.3, so a more modern measuring metric known as the seismic moment is commonly used.
The largest earthquake ever recorded measured 9.5 on the Richter scale, and occurred in Chile, but caused damage as far away as Hawaii due to tsunamis.
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