Earthquakes: Causes, Effects, and Classifications - Terminologies of Earthquake: Measuring Earthquakes: Focus, Epicenter, and Seismic Waves

Earthquakes:

Earthquakes are vibrations, caused by the movement of tectonic plates. These tectonic plates move against each other along the fault and cause vibrations. The movement of these tectonic plates is known as seismic activity, which is another name for earthquakes.

Effects of Earthquakes:

Earthquakes can be very devastating, as they can destroy buildings, injure people, destroy underground infrastructures, cause landslides, avalanches, tsunamis, and cause rivers to change courses. Many earthquakes occur on a daily basis, but are very weak to be felt by humans and cause any damage.

Effects of Earthquake:

1. Earthquakes change the course of rivers

2. Earthquakes destroy buildings and as a result people may die.

3. Earthquakes destroy underground passages.

4. Earthquakes can also cause Tsunamis.

Classification of Earthquakes: 

The classification of Earthquakes is based on their mode of origin.

1. Earthquake due to Surface cause:

This type of earthquake is caused due to the land slides and collapse of underground passages in cities. They are very minor and not very disastrous.

2. Earthquake due to volcanic cause: 

Volcanic eruptions are also a cause of earthquakes. However, they are very feeble.

3. Earthquake due to tectonic cause:

They are the most disastrous and the most numerous around the world. They are caused by the movements of tectonic plates along the fault. 

Terminologies of Earthquake:

Focus:

It is the point under the crust of the earth where the seismic activity or earthquake radiates in all directions.

Epicentre:

Epicentre is located vertically above the focus on the surface of the earth from where the earthquake starts, and its intensity is the greatest in epicentre.

Iso Seismic waves:

These are the lines, connecting the points of equal intensity on the ground surface. 

Earthquake Intensity: 

It is measured according to the destruction caused by the earthquake. It is expressed as a number given in earthquake intensity scale or richter scale.

Tsunamis: 

They are the gigantic waves produced by earthquakes underwater. They cause a lot of destruction to the areas near shore.Their length can stretch up to 200 km and they can travel at 800 km per hour.

Seismographs: 

They are the instruments that are used to detect and record earthquake waves.