According to a report by CNN Portugal, people should not be alarmed.

Luis Matias, professor of Geophysics at the University of Sciences and researcher at the Geophysics Center of the University of Lisbon, told CNN Portugal that there is no scientific evidence that suggests a direct relationship between successive earthquakes. Furthermore, they are relatively small earthquakes and “small earthquakes can occur anywhere”.

“The Earth's lithosphere is subject to constant forces and, at points that we cannot predict, the accumulated tension can lead to small earthquakes,” he explains.

“It is important to understand the difference between small earthquakes, such as those recorded in the Algarve, and large earthquakes, which can represent a significant threat”, continues Luis Matias. “Large earthquakes, normally associated with major tectonic faults, are the ones that deserve our special attention.” These faults, such as the famous San Andreas Fault in California (USA), are “places where tectonic plates are under great tension” and eventually generate an earthquake of great magnitude.

On the other hand, “small earthquakes, such as those of magnitude 3 or 3.7, are much more common and can occur anywhere. Normally they go unnoticed by most people, but when felt they can provoke some reaction from the population.”

Luis Matias describes a "useful analogy" to understand smaller earthquakes: “It is to imagine the Earth's lithosphere as a pile of sand. Now, when grains of sand are dropped one by one into the pile, eventually one grain can trigger an avalanche. This avalanche can be small or large, depending on the size of the pile of sand and the energy released.” Likewise, “smaller earthquakes are like individual grains of sand, which occasionally fall and cause small tremors, while larger earthquakes are avalanches that occur along large tectonic faults”.

Therefore: “Small earthquakes are relatively common and are not necessarily indicative of an imminent threat.”

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