[ad_1]
After the 6.7 Richter on Friday October 30, Samos and its surroundings continue to vibrate, almost non-stop. About 150 aftershocks of varying intensity have been recorded. On average, every 17 minutes there is an earthquake of magnitude 3.4, with the highest vibration reaching 5 R. This is the image of terror and agony that the people of Samos experience the first three 24 hours after the main catastrophic earthquake. on Friday. Seismologists from the get-go warned of strong aftershocks, even above 6 Richter.
In the instant, in Karlovasi de Samos And while the earth still trembles beneath your feet the executives of the Laboratory of Statistics and Data Analysis (LabSTADA) of the Department of Statistics and Actuarial-Financial Mathematics of the University of the Aegean, monitors, records and analyzes post-earthquake activity. In more detail, according to an announcement from the Laboratory, 10/30/2020 and time 14:04 pm when the first earthquake occurred, until 01/11/2020 at 3:28 pm the number of replicas is 147. The minimum value the magnitude of the vibrations is 2.4R, while the maximum is 5R. The mean distance between earthquakes is 17 minutes, while the mean distance is 12.5 minutes. On average, each post-earthquake vibration reaches 3.4R. The first 24 hours, an average of 3.5R aftershocks occurred every 15.5 minutes. The second 24 hours, according to MO every 20 minutes there was a 3.2R aftershock.
THE great earthquake, the one the experts expected, has not yet manifested, although the vibrations continue. For example, at 10:53 p.m. on Sunday, November 1, there was an earthquake of magnitude 3.3, with epicenter 32 km northeast of Samos, that is, very close to the coast of Asia Minor, but at a focal depth greater than twice the main vibration, 25 km.
The main seismic earthquake that occurred at 11:51:24 “on Friday, October 30, measured at 6.7 Richter. The epicenter, according to the Geodynamic Institute of the National Observatory of Athens, was 11.8 kilometers north of Samos, in the maritime zone between the Greek island and its cape. from the Turkish province of Seferichar. Until a few years ago, this information was sufficient to inform the public. Today, however, since our country is the most seismic Europe and the sixth in the world, Greek citizens have been trained to require additional data.
Asking for answers to questions like «Was this the main earthquake or is it expected to be even stronger? If it was the main earthquake, what about the aftershocks? Are there other activated faults besides the one that caused today’s earthquake? If so, are we entering a period of intense and continuous seismic activity? What was the focal depth? And how did this affect the wave that drowned the port of Samos? Because suddenly we talk for ‘tsunami’ in Greece?»
The questions are not only crucial, but also vital: Friday’s earthquake was felt across Greece. Then, automatically, all the citizens of the country experience almost the same agony as the inhabitants of Samos, where there was the greatest disaster. And, sadly, dead and wounded. Of course, the picture is much more tragic on the opposite coast, in Turkey. The negligence of the neighbors regarding the seismic specifications of the buildings compared to what is valid in Greece in recent years, is a factor that is emphasized in all similar incidents. But nevertheless, that the same earthquake hit the Smyrna area much harder than Samos, is a fact that is related to the characteristics of the specific geological phenomenon.
Because the displacement of the colossal stone masses, the collisions and the rearrangement of the fault somewhere deep in the earth’s crust, below the bottom of the Aegean, caused the release of seismic energy. His direction was the coast of Asia Minor, which struck with terrifying severity, this time. Unable to predict what will happen next, in the same area.
Regarding its typology, the 6.7 magnitude earthquake on Friday 10/30 is described as “superficial”, since its focal depth was very small – “only” 11.8 km. If the epicenter of the earthquake, that is, the point where the subsurface balance was altered causing the vibration, were more than 60 and up to 300 km, then the earthquake would be characterized as an intermediate depth.
Focal depth, or the distance between the actual focus and its epicenter, as found on the Earth’s surface, has a decisive (but not exclusive) effect on the intensity of the earthquake. By oversimplifying, the smaller the focal depth, the more intense the vibration, the greater the damage to buildings, structures, etc. That is why seismologists are particularly concerned about surface earthquakes, since the phenomena of this followed by intense post-seismic activity.
In other words, after a large earthquake on the surface, experts expect many strong earthquakes. In this case, for Samos, seismologists predict a sequence of vibrations above 6 Richter and for a period that can last several weeks, possibly more than a month. However, concern for the following is compounded by Egelados’ inaction: Although there were aftershocks, they were not of the intensity that seismologists expect to consider that the phenomenon is evolving according to the usual pattern. Of course, in the great Kos earthquake in 2017, no strong aftershocks were registered, whatever that means.
Tsunami in the Aegean?
As scientists repeat, no earthquake is the same as another. However, as a supervisory example, it is recalled that The Kos earthquake in July 2017 was magnitude 6.6 Richter, with a focal depth of about 7 km, less than in Samos. The sea gravity wave (tsunami) reached a height of 1.5 m, roughly the same as the one that followed the earthquake on Friday. Especially because of this phenomenon, which seems foreign to the Greek -or Mediterranean- data, the academic and professor of Natural Disasters Mr. Konstantinos Synolakis has repeatedly warned that appear in our country.
After the earthquake in Samos, Mr. Synolakis spoke about the similarities of the new tsunami to the one in Kos and wondered if the cause was an underwater landslide, apparently due to the earthquake. Usually, Tsunamis are waves that occur offshore, as a result of underwater earthquakes (such as the one at Samos) or landslides, or a combination of these causes. The size of the tsunami depends on the depth of the sea area. Thus, outdoors, the speed of the waves that rise is very high (up to 800 km / h). In shallow waters, the speed of tsunamis decreases, but their height generally increases.
In any case, as underlines the professor of Geophysics of AUTh Mr. Konstantinos Papazachos “We are talking about local tsunamis, not so much because of the earthquake, but because of the underwater activity. They have nothing to do with those of the Pacific, for example, where gravity waves strike at great distances and after hours. In Greece, when earthquakes occur a short distance from the coast, the waves appear in a very short time, generally in less than 5 minutes ”. Thus, the beaches of Samos are not threatened with destruction by a new tsunami, which will rise after a possible strong earthquake. But even a small tsunami can surprise and seduce people, who tend to ignore or underestimate its deadly power.
Geological plates
Despite progress, seismology or geophysical sciences in general remain imperfect and practically defenseless. to make safe predictions. Ultimately, the only indisputable knowledge is that earthquakes occur in groups and never individually. And also that the Earth is not a static monolith. Inside, from the outer crust, the lithosphere where earthquakes occur, to the center of fire at its core, the human planet is in constant internal turmoil.
Focusing on the area of the recent earthquake, experts are reluctant to predict what will follow, whether the vibration will cause dominoes, whether adjacent faults will be activated, etc. As Mr. Papazahos says “this area is known, has major faults, which have led to earthquakes in the recent past. Samos is surrounded by two large exogenous zones, one to the north and the other to the east of the island, towards the coasts of Asia Minor. We do not know about these faults if they are more or less ripe for an earthquake. At this stage we deal with the sequence of the main earthquake and the extensions of the fault itself. A piece by his side may break tomorrow, the day after tomorrow or in a few days, to give a strong earthquake and cause equally great damage to already overloaded buildings ”.
The epicenter of the earthquake that struck Samos not unknown to seismologists, although this is the first time such a strong vibration has occurred there. Of course, the wider region, and especially the Turkish side, is extremely seismic, so the 6.7 Richter did not surprise scientists. However, the fact that the earthquake was felt throughout Greece, which is explained by processes that do not stop evolving in the lithosphere or in the upper geological layer of the planet.
To understand the root causes of earthquakes, you have to imagine the whole Earth as a global puzzle, with vast pieces that touch, but at the same time remain in constant motion. These pieces are called “plates” and appear to float, at infinitesimal speed, in the lower and less solid layers of the planet.
Greek the space is located right on the boundary between the north, Eurasian and African plate. These plates are in a delicate dynamic equilibrium, while at the same time our country is affected by smaller geological formations (smaller “plates”), which compress, collide and drag one another. Sometimes they crack or break into smaller parts, crack and rearrange themselves in a new state of equilibrium, which will also turn out to be temporary and will be nullified by new tectonic events.
Whether they occur in a few years, decades, or millennia, earthquakes will exist as long as there is movement within the Earth. Greece was shaken by the Samos earthquake because a few dozen kilometers underground the Aegean geological subplate has “ridden” the Africa plate, pushing it deep into the Earth’s mantle. The geological substrate of the Aegean Sea is estimated to traverse the African plate at a speed of about 3.5 cm per year. The inconceivable energy produced by the displacements of these giant stone formations is immediately transmitted and shocks Greece as a whole. As has been the case with earthquakes for millions of years.
News Today:
Endless tragedy in Turkey: 76 dead in 6.7 magnitude earthquake
Pandemic-Turkey: more than 2,100 cases and 74 deaths in 24 hours
Daily coronavirus cases in China remain low
