An earthquake is a sudden movement of the earth’s crust that is produced by the release of accumulated energy through the faults formed between the tectonic plates.
Earthquake is synonymous with earthquake. However, although earthquake and earthquake refer to the same phenomenon, the use of both in popular language is different, depending on the impact with which a seismic movement is perceived, usually determined by the effects of its degree of magnitude and intensity level .
|It is a sudden movement of the earth’s crust that occurs when there is a release of energy caused by rock fractures where the tectonic plates meet. It is also known as: “earthquake”, “earthquake”, “tremor” and, to a lesser extent, “shaking”.
|An earthquake is the same as an earthquake. However, in popular language and in different regions it is so called when, due to its degree of magnitude, its effects cause more serious damage and it is perceived with greater intensity.
What is an earthquake?
An earthquake is a sudden breakdown of rocks at the meeting points of the tectonic plates (faults), in the interior of the Earth. This sudden release of energy spreads in the form of waves that cause the ground to move. Popularly, an earthquake refers to a less intense earthquake.
The word earthquake comes from the Greek seismós and means ‘earthquake’, being a Spanish adaptation of the French seismos . In Latin America the word “seism” is used more frequently, while in Spain it is more common to use “seism”. Other words used to refer to a light or low intensity earthquake are “tremor” and “shaking”.
Characteristics of earthquakes
The characteristics of light or low intensity earthquakes are:
- It is not possible to predict where they will occur, their duration, magnitude or intensity.
- They have a short duration and this varies according to the place of measurement and distance from the epicenter, the instruments used and the perception of those who feel them.
- Slight damage.
What is an earthquake?
Earthquake and earthquake are synonymous and refer to the same phenomenon. However, in several Spanish – speaking countries , “earthquake” and “earthquake” are used differently, depending on the effects that this movement of the earth produces and how they are perceived.
The word earthquake comes from the Latin terraemotus , composed of terra , which means ‘earth’, and motus , which means ‘movement’, so an earthquake is a movement of the earth.
Generally, an earthquake is considered to cause serious material damage and involves the presence of fatalities . The intensity and magnitude with which the presence of an earthquake is measured can vary from one region to another.
Characteristics of earthquakes
Since earthquakes are earthquakes, perceived with a higher intensity, they have the same general characteristics as light or low intensity earthquakes.
Among the characteristics associated with earthquakes are:
- The presence of serious material and economic damage.
- The loss of human life.
Causes and consequences of an earthquake
Causes of a telluric movement
Earthquakes or earthquakes are mainly caused by the displacement of the tectonic plates that make up the lithosphere.
This displacement produces energy that accumulates at the meeting point of various tectonic plates. The plates move because they float on a mantle of liquid rock. When the accumulated energy is released, it exceeds the elasticity limit of a rock and ends up fracturing it.
These fractures in the rocks generate faults and seismic waves originate from the hypocenter (the focus of the earthquake inside the ground). The hypocenter of an earthquake can reach up to 700 km deep.
The earthquakes that occur in the faults represent the vast majority of seismic events on the planet.
Other causes of earthquakes can be volcanic eruptions, erosion of material within the soil, and large material displacements caused by landslides in mountains.
Consequences of a telluric movement
An earthquake or earthquake can cause both material and psychological damage to people as a result of the human and economic losses that they generate.
Among the material effects that result from an earthquake are the damage and destruction of buildings, such as houses, buildings and the road system. There is also the negative economic impact caused by the damage to food production centers, the paralysis of basic services and shops.
In developed countries, the intensity of earthquakes and their effects can be mitigated to some extent. In countries where there is a high degree of poverty and a higher population density, the negative consequences can be more devastating.
As for the psychological effects , these can manifest themselves in the form of post-traumatic stress, feelings of insecurity, depression, anxiety and panic.
If the earthquake has a high intensity level, it can cause the loss of a large number of human lives .
Countries with the greatest presence of earthquakes
It is in the countries located in the Pacific Ring of Fire where there is the greatest seismic activity, around 80% of the strongest earthquakes in the world occur there.
Countries such as Chile, Peru, Costa Rica, Mexico, the United States (west coast), Canada, Russia, Japan, Indonesia, Malaysia and New Zealand, suffer great disasters due to the presence of earthquakes.
This occurs due to the existence of 10 tectonic plates distributed around the Pacific Ocean. These plates are in constant motion, converging or diverging around their limits, causing collisions or separating between them and constantly changing their shape.
In other countries such as Turkey, Nepal, Pakistan, Iceland, Italy and the Balkan region there are also occurrences of earthquakes with a high destructive degree.
Examples of large earthquakes
Some of the earthquakes that have caused great impact and serious consequences in modern history are:
|May 22, 1960
|December 26, 2004
|Biobío region and Maule region
|February 27, 2010
|August 15, 1950
|September 1, 1923
|October 8, 2005
|July 27, 1976
|September 28, 2018
|1000 – 2000
|Port au Prince, Haiti
|January 12, 2010
|200,000 – 300,000
Magnitude and intensity of a seismic movement
The magnitude of an earthquake is a measure used to determine its size, as it measures the energy released from its focus. This is a unique scale for each seismic occurrence.
The size of an earthquake is measured based on the readings of seismographic records. There are different methods to measure the magnitude of an earthquake, but the best known and most used is the Richter scale , devised by CF Richter in 1935.
This scale is not linear, increasing by a factor of 32 from one point to another. This means that an earthquake with a magnitude of 5 is 32 times stronger than one of 4. The magnitude of an earthquake is classified using an open number from 1, without having a specific maximum limit.
When an earthquake occurs, it is difficult to obtain data on the magnitude immediately, taking about 30 minutes to obtain them, so the preliminary data on the magnitude may differ with the actual magnitude of the earthquake.
The data on the magnitude may also vary depending on the location of the institutes in charge of seismological analysis in different countries.
|Magnitude of the earthquake
|Effects of the magnitude of the earthquake
|Less than 2
|It is not perceptible.
|Between 2 and 3
|It can be perceived, but without causing damage.
|Between 4 and 5
|Movements in buildings and structures, causing some damage.
|Between 6 and 7
|Destruction of great proportions.
|Between 8 and 9
|Total destruction of the place where it occurs.
|10 or more degrees
|One of this magnitude has not been recorded.
The intensity is a qualitative way to measure the perception of the effects of an earthquake and depends on the place in which these effects are observed.
The modified Mercalli scale is the one used to measure the intensity of an earthquake and has 12 values expressed in Roman numerals. Its name comes from the Italian seismologist Giuseppe Mercalli, who was one of the first to propose a way to measure the intensity of earthquakes.
This scale is subjective and depends on the perception of an earthquake and its effects on human settlements in order to determine its intensity.
According to the Mercalli scale, an earthquake that has been felt by sensitive people or at rest, has an intensity level II or III, being considered light or moderate, respectively.
When an earthquake reaches a level VI intensity, there is damage to the structures, but it is still considered a mild earthquake . As of VII, an earthquake causes general destruction of infrastructures, with possible human losses. At this time the earthquake is considered in popular language as an earthquake .
Modified Mercalli scale
|Effects of earthquake intensity
|Very weak earthquake: most people do not perceive it.
|II – III
|Weak and mild earthquake: few people perceive it. There are slight movements of objects and buildings.
|IV – VI
|Moderate or weak earthquake: most people perceive it and have difficulty walking. There is movement of objects and the presence of slight damage.
|VII – VIII
|Strong or very strong earthquake: difficulties in walking and driving vehicles. There is serious damage to buildings and structures.
|IX – X
|Destructive or disastrous earthquake: widespread panic. There is destruction of buildings and structures.
|Very disastrous earthquake: few buildings remain standing and the road structure is seriously affected.
|Catastrophic earthquake: almost no survivors. There is total destruction and great topographic alterations.