The earthquakes that periodically hit the planet, traditionally associated with the boundaries of tectonic plates, are happening in an increasingly unpredictable way, and farther away from the tectonic plate boundaries, as would be expected.
The unpredictability of the place of occurrence and the potential for destruction, in an era when science is supposed to have a greater understanding of the origin of seismic events and a greater ability to anticipate them, is disconcerting, explains BBC Science Focus.
Bill McGuire
Éric Calais, a professor at the École Normale Supérieure in Paris, and Jean François Ritz, a researcher at the CNRS Geosciences Laboratory in Montpellier, are at the forefront of efforts to understand intraplate earthquakes, which occur inside tectonic plates.
This phenomenon is far less understood and significantly more difficult to predict compared to its interplate counterparts, which occur at the boundaries of tectonic plates.
Intra-plate earthquakes, although rare, pose a significant threat due to their unpredictable nature and the potential for substantial damage in regions traditionally considered geologically stable.
Historical occurrences, such as the devastating 2001 Bhuj earthquake in India, which killed around 20,000 people, and the 1886 Charleston earthquake in the USA, highlight the potential for massive loss of life and material damage, even in areas not usually associated with seismic activity.
These earthquakes, which occur due to the accumulation and sudden release of stress along geological faults within the plate, can have a remote origin in seemingly harmless events, such as ruptures caused by pressure equivalent to a handshake.
Unlike earthquakes at plate boundaries, where the accumulation of stress is monitored and somewhat predictable, intra-plate faults are often unknown until ruptures occur, making it virtually impossible to predict when or where the next event will occur.
The mechanisms that trigger these earthquakes can vary - from natural processes such as the melting of glaciers and erosion of mountain ranges, to human activities such as mining.
In recent studies, Calais and Ritz have focused on understanding the triggers behind intraplate earthquakes, such as the 2019 Le Teil earthquake in France, which the researchers believe was induced by the melting of a polar cap and eventually aggravated by human activity in local quarries.
According to the two researchers, climate change and human activity at key points in the tectonic plate system can increase the frequency of intra-plate earthquakes - with an ever greater impact on populations, especially as urbanization increases in risk areas.
Cities such as Basel in Switzerland and Charleston in the USA, now with significantly larger populations living in more vulnerable buildings compared to those that existed at the time some historic earthquakes occurred, have an increased potential for disaster.
Thus, the researchers stress, as the planet continues to warm, understanding the link between climate change and seismic activity becomes increasingly crucial to protect future generations from the sudden fury of any seismic event in an unexpected location.
