Measurement

There are two main types of scales that are used to measure earthquakes. The Richter scale, and the Mercalli scale.

The Richter scale is one of the scales that is used to measure earthquakes. It is most commonly used in the United States, where as the Mercalli scale is used more globally.

The Richter scale was invented by Charles Francis Richter.

Charles Francis Richter was born on April 26 th 1900 in Hamilton Idaho. He was an American seismologist which is a person that studies earthquakes. He is most commonly known as the creator of the Richter scale, which was first used in 1935. He created the scale with his longtime friend Beno Gutenberg. He studied at the University of Southern California; and went to the California Institute of Technology in 1936.
The Richter has nine different levels of earthquake severity. The Richter scale is a logarithmic scale, meaning that each level on the scale is actually ten points away from the other. Levels one and two, are most generally not felt by people, and are normally only sensed by sensitive seismographs. Even though they are not felt, they are still recorded.

Levels 3 to 5.5 are usually felt by people as well as seismographs, but do not cause as much damage or movement as those higher on the scale. Usually, an earthquake in this range only causes such movement as slight shaking of glass, or perhaps a hanging picture falling off onto the floor.

An earthquake that is from the range of 5.5 to 6.0, only causes slight damage to well designed and new buildings, but can cause from slight to severe damage to old or poorly constructed buildings within a certain area limit.

Earthquakes that are in-between 6.1 and 6.9 can be very destructive to any buildings (either old or new) within an area of 100 Kilometers away from the center of the earthquake.

And last but not least, earthquakes that are above 7.0 are considered major earthquakes. They can cause from severe damage buildings as far as several hundred Kilometers away, as well as cause furniture to fall over and break.

The Richter scale, is used to rate the magnitude of the earthquake. This means, it rates the amount of energy that is released during the quake. To find the magnitude, scientists find the amplitude of the largest seismic wave that is recorded on the seismographs during the earthquake.

To find the amplitude, they measure how far the distance is from the midpoint of the wave to the center of the crest (top).

Once done, the scientists are able to determine how high that earthquake is on the scale.

The Mercalli scale is another type of scale that is used to measure earthquakes and their severity. Unlike the Rictor Scale, this scale is used more in the different parts of the world instead of in just the United States . Unlike the Richter scale, the Mercalli scale has 12 different levels of severity instead of only 9. Here is the scale in its entirety:

Number on the scale Damage and effects

1. Detected only by seismographs
2. Noticed only by sensitive people
3. Vibrations caused by heavy traffic
4. Usually felt by people standing. Rocking of free standing objects.
5. Sleepers awakened.
6. Trees sway, some damage from falling objects
7. General alarm, walls crack
8. Chimneys fall and there is some damage to buildings.
9. The ground starts to crack, houses start to fall, and pipes break.
10. Ground badly cracked and many buildings destroyed. Some possible landslides.
11. Few buildings remain standing, bridges destroyed, water, gas, electricity, and telephones become cut off.

12. Total destruction, objects are thrown into the air, much shaking, ground becomes cracked in many places. Tsunamis can also be created at this point.

Unlike the Richter scale, the Mercalli scale cannot be detected by seismographs. In order to find out the exact number the earthquake is on the scale, scientists and investigators must interview eyewitnesses, as well as examine the scene where it happened. Once they have a good idea of the amount of damage caused, they are able to determine the number that earthquake is on the scale.