There are several cities around the world that experience small tremors called microseisms. The fact that they occur spontaneously and sporadically doesn't raise any alarms, but when these micro-earthquakes happen continuously, that's when they alert the population.
This movement is caused by the convergence of tectonic plates, but in other cases it occurs due to volcanic activity in the area. However, it is essential to understand other possible consequences, as it is necessary to know its origin.
What are microseisms?
Microseisms are small tremors or mini- earthquakes that occur on the Earth's surface. They generally go unnoticed or are negligible, and they often serve as a warning that something may be about to happen, such as a volcanic eruption.
When these microseisms occur, they are usually associated with the movement and convergence of tectonic plates. Sometimes they are related to volcanic activity in the area. This can indicate an impending volcanic eruption, which may be harmless or catastrophic.
In other cases, it can be associated with an accumulation of energy beneath the earth, often caused by the phenomenon described above. In the context of earthquakes, it is essential to understand how these natural forces affect our planet, a topic explored in greater depth in the article on place, time, and space.
Are these microseisms dangerous?
Microseisms do not usually pose a significant risk. They are small tremors with a minimum magnitude on the Richter scale, between 2.0 and 3.0. Given this, their potential to cause damage is minimal or nonexistent, but people who feel these tremors may experience anxiety.
To understand the magnitude of these movements in more detail, there is a list of earthquake levels and their repercussions within society. According to many universities, knowing this data is important for categorizing them.
- 3.5 - 5.4 It is often felt, but causes only minor damage.
- 5.5 - 6.0 Causes light damage to buildings.
- 6.1 - 6.9 It can cause severe damage in highly populated areas.
- 7.0 - 7.9 Major earthquake. Causes serious damage.
- 8 or greater Great earthquake. Total destruction of nearby communities.
When these microseisms occur, the damage is almost nonexistent. They are not even perceptible up to 8 kilometers from the epicenter, so they are harmless. In the context of this natural phenomenon, microseisms can be a sign of seismic activity that will affect the region, something closely related to the study of [missing information].
There are areas on our planet where these movements are constant due to their location in a conflict zone. They manifest in environments of intense seismic activity or within a Trans-Mexican Volcanic Belt.
Do microseisms exist in Spain?
In reality, they exist in many parts of the world, especially in Mexico. Within Spain, there are areas with a higher seismic risk that don't usually lead to major earthquakes. Below, we detail the most problematic areas, given that two tectonic plates converge in our country: the Eurasian and the African.
- northeast zone, in the Pyrenean mountain range, due to the Pyrenean fault.
- In the south, in the area of Andalusia, Murcia and Granada, due to the African plate under the Eurasian plate.
- In the Canary Islands, due to its volcanic origin. In this area, patterns of microearthquakes are recorded, especially on the island of El Hierro. This tectonic activity is also detected between the island area of Tenerife and Gran Canaria.
Small earthquakes and microseisms recorded in Spain
There is an official website that records micro-earthquakes that have occurred in the last 10 days. It's a table that shows where they have occurred and their magnitude. Obviously, these types of tremors do not exceed 2,5 on the Richter scale.
There are reports from Spain of multiple tremors that have astonished scientists. We have observed this in Asturias and León, with 45 micro-earthquakes occurring beneath the Cantabrian Mountains at a depth of 18 kilometers.
This event occurs along the Ventaniella fault , which runs for 400 kilometers between the western coast of Asturias and the Duero River basin. Between 2015 and 2017, a total of 45 earthquakes occurred, all with a magnitude of less than 2 on the Richter scale.
The epicenters were located beneath the Cantabrian Mountains , between Asturias and León. They were at a depth of 18 kilometers, so they could not be detected by local residents.
Mount Teide also registers more than 600 microseisms at times, a type of activity expected in an area of active volcanic islands. These tremors may foreshadow an eruptive process in the near future.
In the Tenerife area, up to 630 small-magnitude seismic events were recorded just a few years ago. These tremors were located between 9 and 12 kilometers deep, according to the Canary Islands Volcanological Institute (INVOLCAN).
In this case, the microseisms in the Canary Islands are related to its volcanic nature. In other cases, this activity arises from being in an area prone to faults or subsidence caused by soft soils. This activity is caused by pressure on the faults themselves and, in some cases, is more noticeable to the local population.
Different tremors, magnitudes and consequences
Earthquakes of magnitude less than 2 are called microseisms. They are barely perceptible, and up to 8.000 occur daily. Earthquakes of magnitude 2 to 2,9 are considered minor and are almost perceptible. Up to 1.000 tremors occur daily.
The largest earthquake in recorded history occurred on May 22, 1960. It struck the city of Valdivia, Chile, and registered a magnitude of 9,6. It is one of the most violent earthquakes ever recorded on Earth, although magnitudes on the Richter scale range up to 6,9. These values are not measured by intensity, as intensity often depends on the distance from the epicenter rather than the magnitude itself. If such a tremor occurs near the surface and in a location susceptible to earthquakes, the consequences can be fatal.
There are magnitudes beyond imagination; a magnitude 10 earthquake would be apocalyptic or legendary. Earthquakes of magnitude 32 even exist, but they only occur on the surface of the sun. Other seismic events can be impressive on our planet; very rare earthquakes of magnitude 9-9,9 have been recorded . These are devastating, affecting thousands of kilometers, and occur about once or twice every 20 years.
