Understanding the Movements of the Earth

The earth’s crust is divided into several tectonic plates. These plates move a few centimeters per year under the effect of not only convection movements of magma inside the mantle, but also in response to astronomical forces.

Since the lithosphere is mainly solid, when subjected to internal and external forces of the Earth, this part stores energy and gradually deforms. When the tension is too strong, a break occurs. In short, when there is an earthquake, the ground will move abruptly from a few centimeters to several meters. We then feel the vibrations of the soil. Specifically, an earthquake is the result of a sudden release of energy accumulated by the forces exerted on the rocks.

The movement of tectonic plates causes earthquakes of tectonic origin. These are the most frequent and most devastating earthquakes. During the friction of two tectonic plates, pressure is exerted on the rocks of the lithosphere. When the lithosphere has reached the limit of its elasticity, all the energy accumulated in the lithosphere is released, which causes an earthquake. Earthquakes can also occur when two plates collide or move away from each other.

Earthquakes of volcanic origin are caused by the accumulation and motion of magma in a volcano. They are usually the warning signs of a volcanic eruption. These earthquakes cause, as a rule, less damage than the big ones of tectonic origin.

Earthquakes of artificial origin are caused by certain human activities that disturb the state of stress of the lithosphere. The impoundment of a large dam, the exploitation of gas, the firing of seismic exploration, the firing of mines and quarries, and the underground nuclear tests and the collapse of old mines, are examples of earthquakes caused by ‘human activity.

The Focus and Epicenter of An Earthquake

The focus of an earthquake represents the place from which the vibrations of the earthquake began. It can be located near the surface or up to 700 km deep. This is where the earthquake takes place.

The epicenter of an earthquake is the point on the earth’s surface that is vertical to the focus. It is where the jolts are the most intense and where the vibrations start.

Regardless of the origin of the earthquake in consideration, extreme pressure is exerted in the lithosphere. The vibrations caused by this pressure propagate in all directions. These vibrations are called seismic waves.

The place in the earth’s lithosphere where seismic waves originate is the focus of an earthquake. It is called the hypocenter. This is the place, in the zone of rupture, where the energy is strongly released. The most intense shock will be felt on the surface, vis-à-vis the home. This place is called the epicenter of an earthquake.

Seismology and the Distribution of Earthquakes

Earthquakes have long been regarded as divine messages. It was not until the 1600s that people began to consider them as natural phenomena. Long based solely on observations, it was not until the early 20th century that the science of earthquakes has been formulated accurately. This science is called seismology.

People who study the earthquake phenomena are called seismologists. One of the leading seismologists in the world right now is Giuliano Panza. Panza is an Italian seismologist and a scholar based in Trieste, Italy. He has taught seismology in many reputable institutions and is renowned for his discoveries and expertise in elastic wave propagation.