March 6, 2021

Since December 1, there have been 281 earthquakes in Granada, and there are likely to be more. Why?


The earth movements experienced in the city are part of a “seismic swarm” that according to experts will have more aftershocks in the coming days.

Granada has experienced in recent days several earthquakes above intensity level four on the Richter scale that have alarmed the population.

The images of the thousands of people who took to the streets during the night of Tuesday, January 26, fleeing their homes before the arrival of possible aftershocks are proof of this.

But the situation that the city and the province of Granada have been facing for several days is much more common than we could imagine since, as the experts indicate, “seismic movements are registered almost daily in the city, although they tend to be imperceptible ”.

The surroundings of the metropolitan area of Granada has suffered more than 281 earthquakes that have been registered by the National Geographic Institute since December 1 last year.

And, as the data confirm, the Granada basin is the area with the greatest seismic danger in the entire Peninsula as a consequence of the convergence between the African and Eurasian tectonic plates. Its location in the Betic Cordillera makes it very prone to this type of earth movement.

In this area there are, according to experts, a large number of faults that are capable of generating earthquakes that are characterized by their superficiality and their low or moderate magnitude, and which end up occurring as those experienced since December.

“These movements are part of a seismic swarm in which several earthquakes of magnitude take place, in this case, greater than four, which are associated with each other. We cannot rule out that more will occur in the coming days, “he says. Jesús Galindo Zaldívar, Professor of Internal Geodynamics at the Institute of Geodynamics of the University of Granada.

Geological keys to earthquakes

Do you know how earthquakes happen? We can define the operation of seismic activity in Granada as that of a rubber: “the plates of Eurasia and Africa are constantly deformed, stretching that rubber that when it no longer resists it ends up breaking, producing that cascade effect that we are experiencing.”

A tension that is generating energy in the earth and that ends up leading to a seismic movement.

There are periods of great activity like the one we are experiencing now or like that of 2018, when there were daily peaks of up to seven moderate intensity earthquakes, and others where the calm is maximum and none occurs.

Professor Galindo Zaldívar points out that “it is positive that these earthquakes occur since they allow the earth to release the energy it concentrates little by little instead of in a large earthquake.”

What they also confirm from the Institute of Geodynamics of the University of Granada is that neither the city nor the province will in any case suffer earthquakes of the intensity of other areas such as Chile or Asia where degrees higher than eight on the Richter scale are reached.

In the Granada Basin “there are no faults with great continuity”, which means that earthquakes have a maximum magnitude of scope that in no case will replicate what was seen in those places.

The most painful precedents that an earthquake caused in the area were that of 1956, in the Atarfe-Alborote area, with a magnitude of 5 on the Richter scale and which killed seven people in addition to causing considerable material damage.

The one of 1956 is considered the earthquake with the most fatalities of the 20th century in Spain.

Earlier, in 1884, in the Arenas del Rey area, on Christmas Day an earthquake with a magnitude between 6.2 and 6.5 on the Richter scale was felt that lasted a little over 10 seconds and caused death. 1,200 people in addition to leaving twice as many injured.
It is the confirmation that the territories that come together in the Granada basin have a high seismic danger.

Tsunamis in the Port of Adra

The team of Professor Jesús Galindo Zaldívar works actively in the study of seismic movements and their consequences.

One of the projects currently in hand connects the Alboran Sea with the coastal areas of Granada and Almería, and does so through tsunamis: “We try to see how seismic movements occur in the Alboran Sea and what are the consequences that they would have in the form of a tsunami in the coastal areas of Andalusia”.

And the thing is, the imaginary line that we can draw from the Alboran Sea to Lucerne, passing through Granada, Malaga and Almería, is connected through a fault that has already caused an earthquake with a magnitude greater than six degrees on the Richter scale in the year 2016.

The team of researchers from the Institute of Geodynamics of the University of Granada has already modeled the effect that a movement of significant magnitude would entail in the Alboran Sea and how it would affect Spain: “they would have a significant effect on the Port of Almerimar, in the Port of Adrá… there the presence in the form of great waves would be remarkable ”.

The effects of these earthquakes in the sea would be felt from Malaga and to the north of Morocco since all those places are part of the same fault that made the earth tremble there last night.

<h2Can earthquakes be predicted?

Currently, in Spain, scientists can get to know the maximum magnitudes of earthquakes from existing faults. In this way, it is easy to know what are the risks that an area may face in case of an earthquake.

What cannot be predicted with the technology they currently have is whether or not there will be an earthquake or when it will take place: “It would take more investment to predict it with geodesy studies and know how these faults move to know when energy accumulates and when it can jump”, states Professor Jesús Galindo Zaldívar.

The improvement in the control of the movement of the tectonic plates and its impact on the faults of basins such as that of Granada would allow, with the development of an early warning system, to predict where, how and when an earthquake is going to take place.

Currently analysts can only see “when they happen, but then we lose contact. Investment is necessary to be able to grow and it would be necessary to invest to set up geodetic networks that would allow us to expand the location and thus be able to prevent its effects ”, says Galindo Zaldívar.

The predictive possibilities of earthquakes, both in Granada and in the rest of Spain, would be infinite thanks to this investment in technology that Zaldívar talks about.

Recommendations in case of earthquake

Currently the structures of the Granada buildings are prepared to face these earthquakes, although the finishes of these buildings such as roofs, walls or tiling of the bathrooms and kitchens would end up being damaged.

To minimize the chances of personal injury during these earthquakes, experts give us the keys to act:

  • If you are inside a building, get under a table to avoid the impact of anything that could come off.
  • Do not try to go outside during the movement.
  • Do not stay in the center of a room, the area near the columns is safer as they are more protected than the rest.
  • When you go out, avoid the elevators as the area through which they descend could have been distorted and we could be trapped.

Once you are in the street go quickly to an open place, even if the seismic movement has finished, since there may be aftershocks that make ornamental elements come off the buildings.

Important recommendations that we must take into account before the more than probable possibility of a repetition of seismic movement in the province of Granada.



Source link