Thanks to this case, clues have been found in Indonesia to identify areas at risk: the mystery of the 32-year earthquake.
In 1961, a magnitude 8.5 quake struck the Indonesian island of Sumatra, raising a wall of water that crashed onto beaches near the epicenter, devastating infrastructure and killing thousands.
Today, scientists say that tragedy was a major event for other reasons as well. It was in fact a very special earthquake. Whose assumptions should be dated 32 years before the deadly shock.
What is the earthquake "in slow motion" that can last even decades
The geological phenomenon could be called "slow-slip effect", from the English "slow-slip event". The reference is of course to plate tectonics, the model used by most scholars who deal with Earth sciences, according to which the Earth can be divided into twenty tectonic plates.
Earthquakes arise precisely from the collisions and rubbing between the plates. But there is one case in which earthquakes are not of concern. At least with respect to their immediate implications: the reference is precisely to the slow sliding effect. It occurs when one plate slides under another plate without releasing energy so rapidly and violently that the ground shakes.
The long-term consequences of the "slow-motion earthquake" would, however, be worthy of the attention of scholars: the slow plate could in fact spill the tension on the surrounding geological formations that could in turn release energy, however violently and destructively, somewhere in the vicinity of the initial slip phenomenon.
Why scientists are concerned that an earthquake may occur soon
In 1829, a slow-motion earthquake in Indonesia sank by 10 millimeters per year a land whose downward velocity was, before then, 2 millimeters per year (incredible as it may sound, scientists are able to read such distant events in time through the pattern of corals, it's a bit like counting rings in a tree trunk).
The phenomenon has been linked by Aron Meltzner of Nanyang Technological University to the tremor that shook the region 32 years later.
The assumption should not go unnoticed, because something similar is happening even now Other areas of Indonesia in fact are sinking "a little too fast", stresses the researcher, and would already offer reasons for concern. This is the case of the southern island of Enganno, in Indonesia.
Technology is also racing for a future less exposed to inland hazards: here and here two promising innovations involving our cell phones.
Giuseppe Giordano