Why do earthquakes happen

An earthquake is known as a vibration of the earth caused by a sudden release of energy . Smaller earthquakes release energy equivalent to that produced by lightning, but larger earthquakes can release energy equivalent to all of America’s annual energy consumption and outperform the most powerful atomic explosions.

Earthquakes are usually produced by the sliding of the earth’s crust , which represents the most superficial layer of the earth’s rocky part, on a fault, which is similar to a scar that is generated in the regions where this layer is thinner. As a consequence of deformations and bending in some areas of this surface layer (or lithosphere), elastic energy accumulates, in a phenomenon similar to when an elastic rubber is stretched. Once the rocks reach their deformation limit, they fracture and cause the release of this energy in the form of seismic vibrations , giving rise to earth tremors .

To understand the concept well, it could be compared to throwing a stone into a quiet pond that causes the generation of concentric waves, from the point of origin in all directions. In earthquakes, this point of origin is called the focus or hypocenter and the point on the surface in a vertical line from the hypocenter is called the epicenter. Either way, as soon as these waves are released, they can reach the earth’s surface by shaking the foundations of buildings or travel through the interior of the earth horizontally.

After the sudden release of energy from an earthquake, aftershocks of earthquakes can occur , even up to several days later, which are earthquakes weaker than the main one. These replicas are due to the fact that the materials take a while to settle.

You can learn more about this in this other article on What is the epicenter of an earthquake .

There is evidence that the earth’s crust rises (forming ridges), goes into the depths or moves horizontally. These movements can be explained with the theory of plate tectonics . According to this theory, large portions of the crust or tectonic plates move continuously and slowly. Sometimes these plates interact with each other and deform at their edges, giving rise to earthquakes.

These areas of the plates are known as faults and can be very large and generate large earthquakes. This is the case of the great San Andrés fault with 1,300 km and separates the great North American and Pacific plates. However, the most common is that the faults are inactive and do not produce earthquakes.

Although there are many ways to measure the power of earthquakes , the most widely used is the Richter scale . This measures the energy of the surface waves of the earthquake and applies a logarithmic scale, so that each increase in one unit of this scale corresponds to a 32-fold increase in the energy released by an earthquake. Thus, a scale 4 earthquake releases 32 times more energy than a scale 3 earthquake.

It is estimated that a magnitude 4 earthquake releases energy that can be compared to the explosion of 500 kg of dynamite.

Annually, there are about 300,000 earthquakes that are large enough to be felt on the ground, but most earthquakes are small and cause little damage. Of these, only about 75 a year have the capacity to cause significant damage, and many occur in remote areas. Earthquakes that occur near major towns generate earthquakes and liquefaction of solid materials that have devastating effects.

However, the five regions or countries most at risk of devastating earthquakes are:

• California, United States: The great San Andreas fault runs along the west coast of that state and could trigger a major earthquake at any moment
• Chile: it is one of the countries with the most earthquakes in the world. In 1960 it suffered the largest earthquake on record with a magnitude of 9.6 on the Richter scale. The countries of Peru and Chile are surrounded by the great Nazca and South American faults.
• New Zealand: According to experts, the southern islands are the most likely to suffer an earthquake in the next 50 years.
• Manila, Philippines: this country is close to the so-called Pacific Ring of Fire , which also includes territories of Japan.
• Sumatra, Indonesia: A large earthquake with an epicenter off the coast of Sumatra already caused the great tsunami of 2004. It had a magnitude of 9.1 on the Richter scale. If you want to know more about this type of phenomenon, we recommend this other AgroCorrn article on How tsunamis are formed .