Earthquakes: Definition, Types and Distribution

An earthquake is the shaking or trembling of the earth, carved by the sudden movement of a part of the earth's crust.

Types of Earthquakes

Depending on the factors conditioning them earthquakes can be divided into three main groups:

Volcanic Earthquakes: These earthquakes are connected with the processes of volcanism and are thus developed only in the regions of contemporary volcanic activity.

Denudation Earthquakes: or earthquakes due to collapse are the result from the collapse of the considerable masses of rocks, mainly in the mountain regions, the sinking of under-ground cavities. For example Karst Caves and large landslides.

Tectonic Earthquakes: Earthquakes belonging to this group are characterized by maximum force and account for 95% of all earthquakes that are registered. These earthquakes are result of the process of bending (folding) and breaking (Faulting) of crustal mountains concentrated on or near active lithospheric plate boundaries.

Types of Earthquakes depending on the depth at which they emerge.

Surface Earthquakes: With the epicenter at the depth up to 10 Kilometers.

Normal Earthquake: The depth of which varies from 10 to 60 Kilometers.

Intermediate variety Earthquake: Depth varies from 60 to 300 Kilometers.

Deep floor Earthquakes: Whose depth reaches beyond 300 Kilometers.

Distribution of Earthquakes:

Circum Pacific Areas: 70% of earthquakes.

Mid Continental Belt: 20% of earthquakes includes the Mediterranean- Himalayan Belt.

Mid Atlantic Ridge: 10% of earthquakes.

The most commonly quoted magnitude is the Richter scale, devised in 1935 by Charles Richter to indicate the quantity of energy released by a single earthquake. While the Richter scale magnitude is relatively easy for seismologists to calculate, it is not ideal for comparing the sizes of very large earthquakes (magnitude 7 and higher), also known as "local magnitude scale".

The more recently "moment magnitude' is now the most commonly used scale to describe the size of large quakes.

Regions of most of the world earthquakes

Young folded mountains region.

Regions of faulting and fracturing 

Active volcanic regions and

Along the margins of different plates.

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