Mercalli Scale vs. Richter Scale
There is an earthquake usually taking place somewhere in the world every day. The earthquake and its impact is measured either by using the Mercalli scale or the Richter Scale. The two scales, however, each have different applications as well as measurement techniques.
The Mercalli scale has been in existence longer dating back to the 19th century. Its name comes from the modifications made to it in the 1890s by an Italian volcanologist, Giuseppe Mercalli. Ironically, it was Charles Richter who gave the scale its updated form which is used today, presently called the MMI scale, or known as the Modified Mercalli scale.
The Richter scale was developed in 1935 by Charles Richter, along with his associate, Beno Gutenberg, and today it is the commonly used scale in earthquake measurement. It was first developed for use in a particular area of California comparing the size of different quakes in the region. It was later adapted for use around the world. The Richter scale is more objective, but the Mercalli scale is subjective.
The Mercalli scale bases its measurement on the observed effects of the earthquake and describes its intensity. It is a linear measurement. On the other hand, the Richter scale measures the seismic waves, or the energy released, causing the earthquake and describes the quake's magnitude. It is a logarithmic. For example, a magnitude 4 earthquake is 10 times as tense as a magnitude 3 earthquake.
The calculation for the Mercalli scale is quantified from the observation of the earthquake's effect on the earth's surface. It is also based on the effect on humans, objects, and man-made structures. The logarithmic scale for the Richter is base-10 and is based on the amplitude of waves.
The linear scale for the Mercalli ranges from I, meaning not felt, to XII, which is total destruction of the area affected by the quake. The consistency of the scale varies and depends on the distance from the epicenter. On the other hand, the scale on the Richter ranges from 2.0 to 10.0, or higher but has never been recorded. The consistency of the scale varies at different distances from the epicenter, but a single value is given for the quake as a whole.
When comparing the values, VIII on the Mercalli scale is similar to a 6 or 7 on the Richter scale, indicating chimneys falling and there is some damage to buildings. An XI on the Mercalli scale is similar to an 8 on the Richter scale, indicating the destruction of most buildings and bridges.
The Mercalli scale is not as useful for measuring earthquakes, especially in uninhabited areas where the destruction and its strength is not apparent. The scale is considered less scientific because it relies on eyewitness accounts of the loss and destruction caused by the quake. It is, though, useful when comparing two areas where an earthquake occurred.
The Richter scale is a scientific measurement based on the magnitude of the earthquake and allows experts to use more accuracy in comparing the strength of quakes across time and at different locations or even areas of the world.
In summary, the Mercalli scale is less useful than the Richter scale because of its subjectivity versus the Richter's objectivity. The Mercalli scale uses values from I to XII, and the Richter scale's values range from 2.0 to 10.0. The Richter scale is used much more often around the world than the Mercalli scale, which mainly relies on eyewitness accounts of loss and destruction.
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