Most earthquakes last for seconds or minutes, but some can last for hours, days, weeks or even months, and scientists have only recently come close to explaining this phenomenon.
According to the journal Geology, a new study by Dr. Timothy Chapman of the University of New England has identified a key factor triggering these prolonged seismic events. This brings seismologists closer to understanding the nature of slow earthquakes—a phenomenon that has long gone unnoticed but poses a potential threat to residents of seismically active regions.
According to scientists, slow earthquakes, unlike typical earthquakes which are accompanied by sharp and powerful aftershocks, are imperceptible and may last for days or even months, often causing no noticeable movement of the ground. However, their impact on the overall seismic environment and the risks they pose to the population cannot be underestimated.
To understand the mechanism behind this phenomenon, a team of researchers studied rocks on the Earth's surface in New Caledonia, searching for fossil evidence of past slow earthquakes. After examining the samples closely under a microscope, they discovered minute traces indicating the presence of water in the pores of these rocks.
Timothy Chapman says: "This research has studied how water is rapidly made available from solid minerals periodically over thousands or millions of years. Because water is present in the pores of rocks, it provides the low forces needed to cause slow earthquakes, and this may explain the frequency of their activity."
Researchers discovered that a relatively small force is required to trigger a slow-moving earthquake—roughly equivalent to the weight of a full bathtub. Furthermore, the process unfolds in a rhythmic and predictable manner, raising hopes that similar events can be predicted in the future.
Understanding the nature of slow-moving earthquakes is crucial because billions of people live in earthquake-prone areas, and many reside along coastlines threatened by tsunamis triggered by seismic activity.
The researchers point out that despite these advances, the work is far from complete. The next step will involve assessing the extent of rock movement during slow earthquakes and establishing the relationship between the discovered microscopic features and broader geological processes, including the movement of the entire tectonic plate. Finding these "archaeological" features is like looking for a needle in a haystack, because activity lasting only a few days or months can leave minute traces in rocks that took millions of years to form.
