How are earthquakes measured and how massive is the Turkey one?

Source: This post is created based on the article “How are earthquakes measured and how massive is the Turkey one?”, published in Indian Express on 7^th Feb, 2023.

Syllabus Topic: GS Paper 3, Disaster management

News: Recently, an earthquake of magnitude 7.8 struck south-central Turkey and Northwest Syria.

Reports have put the number of fatalities in thousands. This earthquake is of the same magnitude as one that killed about 30,000 people in December 1939.

As per the U.S. Geological Survey (USGS) the quake was centred about 33 km from Gaziantep, around 18 km deep.

Earth’s Mechanism behind earthquakes

Earth’s surface if made up of tectonic plates, which are constantly moving but at a very slow pace. These plates often get stuck or pushing against each other traps the energy. Often this energy is released by the earth in the form of waves, travelling through earth’s crust that results in vibration and lead to earthquakes.

Measurement of the earthquake

Seismographs are used to record earthquakes. When the earth shakes, the recording device on seismographs records the reading of the ground motion. Now these devices works by measuring electronic changes produced by the motion of the ground with respect to the mass.

Magnitude measurement

One of the most important measures of magnitude is Richter Scale. It was devised in 1935 by Charles Francis Richter. One step up in measurement represents a tenfold increase in magnitude. Therefore, an earthquake measuring 7 on the Richter Scale has 10 times the magnitude of one measured 6.

However, Moment Magnitude Scale (denoted as Mw) was developed due to limitations of Richter scale.

Measuring the intensity

Intensity measures the amount of shaking at a particular location. There are Intensity scales, like the Modified Mercalli Scale and the Rossi-Forel scale.

Earthquakes of lower magnitude can be more intense if they are located in more shallow ground or if the area where they occur has more loose soil, etc.

The Modified Mercalli Scale, the most commonly used intensity scale, ranks earthquake intensity on a scale of I. (not felt) to XII. (extreme). The maximum intensity measured in Turkey’s earthquake is IX. or violent.