Can they occur earthquakes in unexpected areas? A scientific study sought to answer this concern. The authors are part of the geosciences area of the University of Utrecht, in the Netherlands.
According to experts, in places like Utah in the United States, Soultz-sous-Forêts in France or the province of Groningen In the Netherlands, seismic movements have been recorded in regions where, according to traditional theory, surface faults should strengthen when activated, thus preventing earthquakes from occurring.
However, research published in Nature Communications reveals that prolonged inactivity of these faults can cause the accumulation of additional stress, capable of being suddenly released in a single seismic event.
The Dr. Ylona van Dintherstudy supervisor, explained that “Flaws can be found practically everywhere. Faults in the shallow subsurface are typically stable, so we do not expect shock movements to occur along them.However, the observed reality contradicts this expectation, since seismic movements usually occur in the first kilometers of the subsoil, precisely where many human activities take place.
The phenomenon is explained by the “fault healing” process, which occurs in those that have remained inactive for millions of years. Although they do not present visible displacements, these faults experience slow growth of the surface that connects them, which increases their internal resistance. This accumulated resistance can, under certain circumstances, trigger a sudden acceleration when the fault activates, thus generating an earthquake in an environment that, in principle, should be stable.
The depth at which these induced earthquakes occur is another risk factor. As they occur no more than several kilometers below the surface, they coincide with the area where human activities are concentrated, which increases the vulnerability of local infrastructure. These quakes are considerably shallower than most natural earthquakes.which can translate into greater destructive potential and the generation of more intense tremors.
A relevant aspect identified by the team of the Utrecht University is that the release of energy accumulated in these faults is usually a unique phenomenon. Once the additional resistance dissipates, seismic activity at that point tends to cease. “As a result, there is no longer any seismic activity at that point.”said Van Dinther. Furthermore, he noted that “the strength of earthquakes, including the maximum predicted magnitude, will gradually decrease”, which implies that the risk of future earthquakes on the same fault is significantly reduced.
The study also highlights that, after the movement of the fault, the already displaced fragments act as a barrier, hindering the propagation of new earthquakes of greater magnitude. This allows the estimated earthquake risk to be reduced, since this risk is determined mainly by the maximum magnitude of the earthquake..
The conclusions of this research have direct implications for the sustainable development of the subsoil. Although it is confirmed that earthquakes can occur on faults considered stable, the probability of recurrence is low once the fault has released its energy, either through an earthquake or gradual slip. The team highlights the need to deepen our understanding of the behavior of faults, particularly whether they will tend to accelerate or slow down, and the role that fault repair plays in seismic dynamics.
The experts of the Utrecht University have begun to develop new calculation models to anticipate and estimate more accurately the risks associated with subsoil exploitation, as well as to improve the communication of these risks to society.
