Earthquake in Turkey: seven keys to understanding the gravity and intensity of these phenomena

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Magnitude, intensity or measurement scales are some of the concepts related to earthquakes, phenomena that occur constantly in the world even if many times they are not even perceived. In exceptional cases they become catastrophes because they exceed a series of thresholds, as happened in the early hours of this Monday Turkey and several neighboring countries.

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Some of the keys to understanding earthquake severity, according to Spain’s National Geographic Institute (IGN), are as follows:

1- How are they produced?

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The areas where earthquakes occur do not look random, they outline stripes that separate the regions. These plates are the outermost part of the planet and move on a fluid layer. This movement causes earthquakes, i.e. sudden ruptures of the earth’s interior. As the plates move apart, they collide and rub sideways, and each movement generates a type of earthquake.

2- What are the most dangerous earthquakes?

When two slabs approach each other, the situation becomes more complicated. Plates collide, warp and stack on top of each other. This is how the largest earthquakes occur, such as the one in Japan in 2011, or the one in Indonesia in 2004, or the one in Chile in 1960. The deepest earthquakes also occur this way, up to 600 kilometers underground.

they are given extreme cases when two continents collide, which generates a chain of mountains like the Himalayas, created by the clash between India and Asia. That collision continues to produce large earthquakes like the one in Nepal in 2015.

Rescuers help an injured girl in an earthquake-destroyed building in the Syrian town of Jandaris on Monday.  Photo: AFP

Rescuers help an injured girl in an earthquake-destroyed building in the Syrian town of Jandaris on Monday. Photo: AFP

3- How do they differ from tidal waves?

Earthquake is a sudden movement of the earth, while tsunami is a sudden movement of water. Tsunami can be generated by a meteorite falling into the ocean, by underwater avalanches and volcanic eruptions, and also by an earthquake on the seabed.

The result is like throwing a stone into a pond, which generates a succession of waves that retreat in all directions on the high seas. Tsunami waves travel at the speed of an airplane, but as they reach the shallow shore they slow against the bottom and move more slowly even though the wave height increases as they approach the beach.

4- What is called seismic magnitude?

The magnitude of an earthquake measures, with the aid of instruments, the energy released by the earthquake. It is a unique and objective value for each earthquake that does not depend on where you are.

5- How are earthquakes measured?

There are different scales depending on the type of earthquake, the measurement system and other factors. The best known is that of Richter (1935), but currently others are used, preferably the moment magnitude scale (Mw), which coincides with that of Richter only in earthquakes with a magnitude lower than 6.9.

Magnitude scales have no stop for their measurement. For example, the 1960 Valdivia (Chile) earthquake had a magnitude of 9.5, and the 2004 Indian Ocean earthquake off the island of Sumatra had a magnitude of 9.3.

6- What is intensity?

The strength of an earthquake indicates how its effect is felt in a place. How people have suffered from it, its impact on objects and damage to buildings. Its value varies depending on the distance from each place where it was felt to the epicenter. Seismological institutes usually give the data of maximum intensity, i.e. how it felt in the most affected place.

7- What are the intensity scales?

There are several scales to measure intensity: the two main ones are the Mercalli Scale and the European Macroseismic Scale (EMS). Both have twelve degrees expressed in Roman numerals from I (very weak or barely felt) to XII (catastrophic or completely devastating).

Source: EFE

Source: Clarin

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