Seismic events, unless they are imperceptible, always have repercussions, not only locally but also internationally. This impact is possibly associated with the unpredictability of seismic events and how devastating the consequences can be depending on their magnitude and, also, according to the vulnerabilities of the affected regions.
What is an earthquake
To better differentiate the terms, we will start with the concept of earthquake. The word earthquake comes from Latin and means ‘earth in motion’ . Theoretically, an earthquake is defined as the sudden and temporary shaking or movement of the earth’s crust as a result of forces originating from the interior of the Earth.
Earthquakes can be measured by their magnitude or intensity. The widely used scale is the local magnitude scale (M) or better known as the Richter scale , which, as its name implies, allows measuring the magnitude of the earthquake. Precisely, according to the magnitude they present, earthquakes can be classified into:
- Micro: magnitude less than 2, they are imperceptible.
- Minor: magnitude range between 2 and 3.9, they are practically imperceptible.
- Light: range of magnitude between 4 to 4.9, it is perceived in the movement of objects. It generally does not cause damage.
- Moderate: magnitude range between 5 and 5.9, can cause structural damage depending on the quality of the buildings.
- Strong: magnitude range between 6 and 6.9, causing considerable damage over large areas of surface.
- Major: magnitude range between 7 and 7.9, causes severe damage in large areas.
- Epic or cataclysm: magnitude range 8 to 9.9, causes devastating damage over a very large surface radius.
- Legendary or apocalyptic: magnitude greater than 10. Fortunately, earthquakes of this magnitude have never been recorded.
Although it is not part of the concept of earthquake, in colloquial language the word earthquake is often used to refer to seismic activity with a magnitude greater than 7.5, that is, according to the description just detailed, they would be those classified as major, epic and legendary. . In turn, the term earthquake is often used when seismic activity has caused injuries or even fatalities and other adverse effects such as damage to buildings and infrastructure.
What is an earthquake
Now that we have learned what an earthquake is, we can continue with the concept of an earthquake. First, it is worth clarifying that in Latin America the word earthquake is used while in Spain there is a certain preference for the word earthquake. Both words, earthquake and earthquake , come from the Greek and mean ‘shake’ .
According to the Royal Spanish Academy (RAE), an earthquake is defined as an earthquake, that is, a sudden movement of the earth’s crust. Consequently, both words are synonymous and conceptually, both earthquake and earthquake can be used interchangeably.
Now, there is a small but marked difference that is not conceptual, but rather colloquial. This difference is around the magnitude of the movement of the earth’s crust. So when is an earthquake and when is it an earthquake? When the seismic activity has a magnitude greater than 7.5 we usually use the term earthquake, while when the seismic activity has a magnitude between approximately 4 and 7 , we usually use the term earthquake.
Meanwhile, this notable colloquial difference associated with the magnitude also brings with it differences in the consequences after seismic activity. As a general rule, it can be deduced that in lower magnitude seismic activities, the consequences will be less after the seismic event. As a result, earthquakes are often linked to those seismic events that do not cause material or economic damage, nor loss of human life .
Finally, let’s see what the word tremor implies. As with the concept of earthquake, the Royal Spanish Academy defines the term tremor as an earthquake or shaking of the earth’s crust . Therefore, conceptually the three terms are synonymous and you can use any of them when you want to refer to a seismic event.
However, here again there is a small colloquial difference and, as in the previous case, this difference is also related to the magnitude of the seismic event. Particularly the term tremor, is used to refer to vibrations or movements of the earth’s crust that have a low magnitude . Consequently, considering only the magnitude of the shock, tremors are closer to earthquakes than earthquakes and colloquially, both tremors and earthquakes are often used synonymously.