The word earthquake comes from the Latin terraemotus (moving earth). Also called an earthquake, it is a sudden movement or shaking of the earth’s crust, produced by internal phenomena somewhere on Earth.

An earthquake originates when rocks subjected to great pressure suddenly break, releasing the accumulated energy, which shakes the ground, propagating the vibrations from its epicenter. Initially, tension may have little effect; but, as they accumulate, the rocks deform at faults and other weak points, eventually breaking. When this occurs, the rock layers rebound and the stored energy is violently released in the form of a seismic shock.

It has been found that most tremors occur along the edges of tectonic plates, which are often also areas of volcanic activity.

The point or focus of origin of an earthquake is called the hypocenter, where the seismic waves arise, propagating in all directions, vibrating the materials through which they spread. The area of ​​the earth’s surface located directly above the hypocenter is called the epicenter and is the place where the earthquake is formed with the greatest intensity.

The effects of an earthquake vary enormously, depending on its strength or intensity, the depth at which it occurs, and the constitution of the ground and subsoil.

The intensity and occurrence of seismic movements are measured with highly sensitive devices to the vibrations of the earth’s crust called seismographs, there are two basic types: one to measure horizontal movements (P waves); and the other, for vertical movements (S waves).

When the earthquakes are not very intense, they are registered only by the devices; On the other hand, when they are very intense they are destructive, causing great catastrophes, especially in constructions such as houses, buildings, roads and bridges. They also cause the loss of many human lives.

In order to better estimate the seismic waves, arbitrary scales have been made, showing various degrees of destructive effects. Such scales are the Richter, Sieberg, Omori, Cancani, Mercalli, and others. The best known are the Richter (magnitude grading) and the Mercalli (intensity grading).

Attempts to predict when and where earthquakes will strike have had some success in recent years. Currently, China, Japan, the former Soviet Union and the United States are the countries that support this research the most.