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How to measure the strength of the earthquake

How to measure the strength of earthquakes

Every year about a million earthquakes occur in the world. A truly strong fluctuations in the Earth's crust occur about once every two weeks.

Most can be found in the wording of the various media: "An earthquake measuring 5.5 ...".

But what lies behind this statement?

In 1935, the American seismologist Charles RichterHe proposed a classification of earthquakes, based on the assessment of the energy released at the epicenter of the tremors. The dimension of energy is called magnitude earthquake. Magnitude - a dimensionless quantity, the maximum value on the Richter scale was 10.0.

To measure the earthquake impact on the environment using the intensity scale.
The most commonly used four assessment of earthquake intensity scale:
1; scale of Medvedev - Shponhoyera - Karnik (MSK-64) -
2; European macroseismic scale (EMS) -
3; Mercalli Scale (MM) -
4; The scale of the Japan Meteorological Agency (JMA).

MSK-64 scale, EMS and MM have twelvedegrees, and seven JMA scale. The intensity of an earthquake is determined by the external signs of destruction. According to MSK-64 scale tremors force 3 points mean weak earthquake, followed by a slight rocking of hanging objects. This description is almost identical with the description of an earthquake intensity of 3 points on the scales EMS and MMS, and roughly corresponds to the intensity of 1-2 points on the JMA scale.

Comparison of the intensity and magnitudeearthquake produced in the process of monitoring and gathering statistical data. Approximate values ​​for the ratio of the centers of earthquakes located at a depth of 30-70 kilometers can be as follows: an earthquake of 6 points on any of the 12-point scale corresponds approximately 2,8-4,3 magnitude on the Richter scale. For example, the magnitude of the Great Chinese earthquake, whose focus was at a depth of 32 kilometers, was about 8.0 on the Richter scale, which corresponds to 11 points on the twelve-point scale. Description for EMS intensity scale is as follows: "The devastating. Almost all the buildings completely destroyed. "

Such strong earthquakes occur about once a year, but the major role played by the location of the epicenter, so many tremors go unnoticed.

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