Why are we shaking so much in northern Chile?

In Chile we are used to constantly feeling tremors, where it already seems like one more anecdote to add to the day when we had to perceive a telluric movement with real concern.

This could be considered a natural reaction, given the fact that more than 20 people can register earthquake newspapers in our country and, even if most of them go unnoticed because they are small, we have the collective feeling of being experts in identifying emergency situations.

One of these days occurred recently, when the National Day celebrations in the north of the country added emotion to the panorama of music and dance of this long weekend.

According to National Seismological Center it was an earthquake magnitude 5.0, which occurred at 1:02 a.m. on Sunday, September 17 and whose epicenter was located 12.3 km northwest of La Higuera, in the Coquimbo region.

Even if the telluric event has not worsened, it reveals an identifiable trend in recent weeks, with the the northern zone as the main center of interest of the majority earthquakes reported day after day.

Overall, there is no cause for alarm, as these are generally events around magnitude 3.0, with a few exceptions above 4.0, according to data from seismology, although a large part of them have their epicenters located near Calama, Ollagüe or Socaire. .

With this scenario, it is appropriate to question the existence of a particular phenomenon, where Experts respond to La Tercera with their impressions on this concern .

For the professor of geology at the University of Desarrollo, Mauricio Calderon These tremors correspond to normal behavior in our territory.

-The sign is that the natural process occurs , which is the process of subduction and is associated with the generation of earthquakes throughout the continental margin of Chile. However, during the last period, the events were concentrated in the northern area of ​​Chile and also in the mountainous area, near the Antofagasta region, in La Puna.

The expert tells La Tercera that the tremors occur closer to the mountainous area, as well as in the underwater area, in response to different terrain processes.

—An interesting aspect that could indicate the predictability of earthquakes, which is a question that is not at all closed, and that there is actually a consensus on their unpredictability, but they are studied under the concept that, Although there are precursor events, before a large earthquake, there are also aftershock processes. , which occur after the major seismic event. So perhaps these events that are happening now are precursors to events that will happen in the coming weeks or months, or will continue to do so.

Regardless, the activity observed so far responds to the characteristics of the northern regions, among which Calderón marks a difference compared to the cities of the south-central area of ​​the country.

—The whole area there from Illapel northward to Iquique, is a seismic zone associated with a segment of the mountain range . It has little to do, for example, with the earthquakes that occur in the south, so to speak, in Concepción, south of Santiago, or in Cobquecura, which are associated with a particular segment of crust . In other words, these are two areas that have different dynamics.

For its part, Luis Donoso geophysicist and seismologist, has also identified projected seismic activity in recent times, as shown in his own analysis disseminated on social networks, even if he recognizes in his analysis delivered to our media that It is an activity positioned within normal limits .

For Donoso, the appearance of what he calls a “sequence” of tremors – excluding the presence of a seismic swarm – must be compared to the activity of previous years, to visualize the future scenario.

—For example, in 2021, southern Huasco experienced two events 5.8 and 5.9 and then an earthquake. Before, we had an earthquake in 2020, in Huasco, of magnitude 7, according to the National Seismological Center. NOW, None of these events allows us to say that a large earthquake is imminent. it’s not going to come out here.

Its point of comparison is the historical archives of the northern zone in seismic matters, where the academic stands out as two major events those which occurred in 1819 -8.5 earthquake in Copiapó- and 1922 -Vallenar earthquake of magnitude 8.5-, events which could be repeated in the future.

—Why is this going to happen again? Because I have the oceanic crust, i.e. the Nazca plate, it is constantly growing at a certain rate per year, which accumulates stress for me. These little earthquakes that form inside me are the irregularities that exist in the contacts between the two crusts and which are triggered suddenly.

When could another major event occur in the northern regions? Donoso says the range considers between 100 and 120 years, counted since the last event in 1922 the dates would therefore coincide with the possibility of a significant movement occurring in the future.

— Then the zone begins to warn, it’s very noble. But these earthquakes cannot mean that an earthquake itself is about to occur. .

According to the academic, attention must be paid to the magnitude of the earthquakes occurring, where several Tremors less than 4.0 magnitude do not mean a threat unlike events of higher intensity which could reproduce the situation observed historically.

— Major earthquakes are predicted. If I had a 7.5, an 8 north of Caldera in the next 3 or 4 years, it would behave like it behaved in 1922. . That would be a sign, be careful, be careful. But it could also be that there is only this earthquake and that in 20 years there will be another one in the southern part.