01/19/2021 10:52
Clarín.com
Society
Updated 01/19/2021 10:56 AM
The 6.4 on the Richter scale earthquake that struck Monday night in San Juan is still causing shock.
The epicenter occurred 54 kilometers southwest of the provincial capital and 112 kilometers north of Mendoza.
Because it took place near the surface, it was felt in other provinces such as Córdoba and the tremor reached even in Buenos Aires.
Although the movement generated panic in the population, and was the
largest scale in more than four decades
, specialists assure that
it was a moderate earthquake
with little impact.
Alejandro Giuliano, director of the National Institute for Seismic Prevention (Inpres), explains that yesterday's earthquake was
the largest -for its location on the Richter scale- since the 1977 earthquake
, also in San Juan, but that it is very far in as to the extent of damage from its predecessor.
The one produced in the 70s had a depth of 17 kilometers and was felt with an intensity of grade IX on the Mercalli scale, and registered a Moment Magnitude (Mw) of
7.4
.
That earthquake caused
65 deaths
(although local authorities currently estimate that there were 125 victims),
destroyed houses and buildings
throughout the region, with an emphasis on the city of Caucete.
The greatest damage occurred in adobe buildings.
Neighbors of Sarmiento spent the night in the street for fear of the collapses.
Photos: Diario Tiempo de San Juan / Natalia Caballero and Walter Vilca
"Compared to the previous one, yesterday's is not such a big earthquake. It is a moderate earthquake that was 8 kilometers deep and
that is why it was felt in several provinces,
" Giuliano details, in dialogue with
Clarín
.
"It must be taken into account that the Richter scale is
logarithmic
, which means that moving from one point to another on the scale means
30 times more energy release
. A 7-point earthquake is 30 times more destructive than the previous one and one 8 points a thousand times. "
And he adds as an example: "If we compare yesterday's with the earthquake in Chile in 2010, the difference is enormous. The earthquake that occurred in Chile had a magnitude of 8.8, that is, it released
4,000 times more energy than the earthquake. yesterday
".
Why it occurs
What is the cause of these earthquakes?
Clarín
asked
.
Giuliano explained that "at the bottom of the South Pacific Ocean, what is called the Nazca plate gets below the South American plate, which is ours, and that generates a
lot of pressure on the crust
."
Giuliano details that the Argentine north is
highly fractured by this issue
.
And he added that in the country there are
about 30 earthquakes per day
, but since they are very deep, they are not perceived.
"The deepest earthquake is less damaging. In Santiago del Estero earthquakes occur all the time, but at a depth of 600 kilometers and that is why they are not felt," he said as an example.
Giuliano explains that aftershocks are linked to the main earthquake and are usually less intense.
"It is generated in a geological fault, which is a wound in the geological crust. Those blocks collide, and it could be that one is getting under the other. In that process, they are accumulating energy until that energy is released and that is what we call an earthquake. Aftershocks occur after the main release of energy and continue until the block, which continues to move, manages to settle into a balanced situation. "
He assures that aftershocks can occur
during the next five days
and that they may not be felt.
"An earthquake can come after the original one that has a greater magnitude. The first is called premonitor. It is something very rare, but it can happen as it happened in 1960 in Chile, which had a magnitude of 9.4".
And he closes by giving a key fact:
large earthquakes occur every 70 or 80 years
.
DD