According to seismologist Paulo Alves , the earthquakes that occurred today, the first measuring 2.4 on the Richter scale at 10:30 am and the second measuring 1.8 at 11:34 am, are aftershocks, since they are “earthquakes very close to the main earthquake”, which occurred “on the edges of the main fault that was activated on Monday”.

Paulo Alves explained that aftershocks, normally, “are at most one degree less than the main earthquake”, remembering that due to the intensity of the earthquake that occurred on Monday, “they probably won’t reach 4 [on the Richter scale]”.

“If we are considering an event like yesterday [Monday], of 4.6, which was felt with an intensity of 5, the aftershocks obviously have a lower intensity, as the earthquake is in the same place, and the energy released is much lower, so that means the intensity will also be lower,” he explained.

In this way, he also added that today's aftershock of 1.8 "was not felt" and, probably, he added that it will be the most common case that "most of the aftershocks of this event, as it was not a very big event, will not even be felt".

According to the seismologist, aftershocks are common and are part of “the reactivation of tensions around the fault field”, considering that “tensions will reorganize and there will be small momentary breaks around the main plane that broke yesterday [Monday]”.

Alves also explained that Monday's earthquake “has nothing to do” with the one that occurred in August last year, which had a magnitude of 5.3 on the Richter scale and occurred 58 kilometres (km) west of Sines, in Setúbal.

“What is common in these earthquakes is the regional tension field, which is similar across the entire Brazilian coast. From the center of Portuguese territory to the south, the regional environment is common”, he highlighted.

The seismologist also said that in the coming days “aftershocks are expected”, highlighting, however, that it is not possible to say that there will be “an earthquake similar to this one, in another region”.

Therefore, Paulo Alves recommends that the population “observe the places where they are most of the time” and know what they have to do, since behaviour can be different depending on where the person is.

The person in charge advised that the Civil Protection guidelines be followed, remembering that, in many institutions, “there are instructions on what to do and that sometimes they can be a little different from case to case if you are on the street, at home, in the car”.