The Aegean Sea is no stranger to earthquakes and rashes. To the south and west of Greece is the deep Hellenic pit, where an ancient piece of dense oceanic crust is being engulfed by the underlying mantle. This descent is not quiet, but chaotic, and the continuous tension on the upper cortex is separating Greece in multiple directions.
This tectonic pandemónium has caused the formation of web -shaped fault areas and a miriad of volcanoes, both underwater and over it. The scientific community, aware of these dangers, remains very vigilant.
Santorini (a gigantic magmatic boiler with two small volcanic islands nested in its submerged center) has a dark and dangerous volcanic history that dates back 650,000 years. In 1560 AC there was a great explosion that ended with a whole civilization, in 726 AD the important explosion occurred and in 1950 there was a small burst. Officially, an active volcanic system is still considered. And it is not alone: in 1650 there was also the explosion of a nearby underwater volcano called Kolumbo that generated a series of high tsunamis and a lethal cloud of toxic gases.
Although it has only been now when the current seismic storm has taken the attention of the media, the truth is that it has been producing for some time. “It began at the end of last year, there began to be more of seismicity, but nobody realized,” explains Isobel Yeo, underwater volcanologist of the National Oceanography Center of Southampton (England).
At the end of January, there was a deep rebound in the power and frequency of these farm; In recent days there have been almost a thousand a day. “It must be a horrible experience,” says Pyle.
The earthquakes do not occur in one place. Although the tremors began in Santorini, the seismic focus quickly moved inside.
The patron of the Ladies does not resemble that of a classical seismic sequence. Often, a failure breaks and produces its strongest earthquake, the main shaking, which follows (normally) a series of increasingly weak aftershocks. But in this case, there is no clear main shaking.
Instead, the region has been shaken by a cornucopia of the very similar seniudes in which, for several days, the fits seemed to be increasingly strong. “This is very unusual,” says Preine.
Compared to the classicAMs, the swarms “do not follow the rules of the game,” says Hubbard. And that hinders the forecast of his future.
In order to speculate on what could happen in the next few days and weeks, we first have to answer a key question. “Are these earthquakes related to volcanic activity or tectonic activity?” Says Preine.
In the first days of this swarm, several Seísas shook the northern boiler of Santorini, the buzzing in the form of a bowl located in the heart of the island. At first, it was feared that this could indicate the beginning of a new magma injection in the cortex, which could generate new harmful or trim.
Fortunately, the boiler -centered tremors were only temporary. “At the moment, the seismic activity is concentrating towards the northeast. It is not grouped under any of the volcanoes we know, ”says Preine. Now, most of the farm come from the area of the Santorini-Amorgos fault, a seabed fragment between the two islands.
These marine earthquakes do not show any of the characteristics of the ascending magma, nor are they accompanied by the typical signs prior to an eruption, such as swelling and soil deformation on the slopes of a volcano. “At this time, it is tectonic activity,” says Yeo, which means that it is something that happens in failures.
Swarms usually associate with fluid movement, such as water or carbon dioxide, through failures. The fluids that escape one fault and invade another can force their opening and cause their break. “They can continue to trigger earthquakes for the simple fact of moving,” says Judith Hubbard, a scientist specializing in earthquakes at Cornell University (in New York, United States).
For now, the main threat is an especially strong earthquake and the consequent landslides or localized tsunamis that may cause. “Santorini may not be about to explode,” says Yeo. But, he adds, that does not mean that a great earthquake can be ruled out.
In fact, that is the reason why schools are closed in Santorini and for which people are urged to avoid the coasts: what is feared is not volcanic activity, but the potential risk of earthquakes and tsunamis.
This swarm could suddenly become extinguished. “But there is still the concern that an acceleration towards a much larger earthquake can occur,” says Pyle. On July 9, 1956, the earthquake of magnitude 7.8 of lovers (the eldest who has shaken Greece in the twentieth century) and the resulting tsunami caused infrastructural damage to several islands, killing dozens of people.
“Living uncertainty as the situation evolves … It is very difficult for people, especially when the buildings fall apart and the earth trembles,” says Amy Donovan, volcanologist and natural risk researcher at the University of Cambridge (England ).
Although a catastrophic earthquake is a matter of concern, it is not the only thing that causes concern. “For the moment, I think that the greatest concern is whether we begin to go more towards the volcanic chain,” says Preine, including the nearby Kolumbo submarine volcano: “There is always the risk of some type of coupling.”
In other words, “if the Magma Chamber is stirred, a volcanic eruption could be triggered,” says Yeo. At the moment, there is no indications that this is happening, but it is something that scientists closely watch.
Instead of based on a pre -existing network of volcanic and tectonic probes, an international team of scientists (led by Greek researchers) is display .
The Greek authorities have communicated the danger to the public in a careful, rapid and transparent way and “they are managing the crisis very well,” says Pyle. But it is disturbing that the near future is not clear. “I am not sure that there is an obvious way that geologists can say: ‘This is the most likely scenario of how it will end.”
(Tagstotranslate) Science
Source link
