There peninsula of the kamchatka It was hit by an earthquake of magnitude 8.8, one of the strongest ever recorded, which also caused waves of tsunami with a maximum height of about 5 meters. Fortunately, at the moment there are no victims but numerous people were injured, especially in Russia – even if after 11 hours the tsunamo alarm returned. The alert remains high in Japan, Peru, Polynesia, And United States, where it is feared for the arrival of any waves of tsunami. But what happened exactly from a geological point of view?
The characteristics of the earthquake and tsunami
Today at 11:24, local time, in Italy on 1: 24 at night, a violent earthquake of magnitude 8.8, about 136 km from the coast and just 20.7 km of depth. I say “just”, because 20 km may seem many but in reality consider that there are selings even at hundreds and hundreds of km deep. And the point is that when the SISMI are so superficial, the rock is not able to absorb all the energy, and therefore they come warned in an intense way also on the surface. In fact, in Kamchatcka the earthquake caused several Damage to buildings: among these also a nursery, collapsed shortly after the first shock. According to the Russian authorities, there would be numerous injured, even if at the time we are writing this content, the overall number of the people involved is not clear. The first shock then followed others, of magnitude between 5.3 And 6.9 and depth between 10 and 30 km: therefore it is a seismic sequence Which, unlike the swarm, contains a main shock, i.e. a greater magnitude earthquake.
But the problem is not only the earthquake itself, but also the tsunami alert that derived from it. In fact, when earthquakes occur in the open sea what happens is that a “step” On the seabed that can perhaps measure only a few millimeters, or perhaps even get to a few meters in the case of the most violent earthquakes, like this. And what breaks what does this do? Moves the entire water columnforming waves high meters that can be reduced on the coasts. Also because these waves propagate in every direction, so in today all the countries overlooking the Pacific are potentially at risk. In many cases, the tsunami alert must be said and then withdrawn after a few hours, fortunately, but in this case the waves have already hit countries like Russia, Japan, And United States, Obviously with variable heights.
The causes from a geological point of view
This is a card created by the USGS, that is, the US body that deals with monitoring the main earthquakes not only in the country but in the world. The red star indicates the epicenter of today’s earthquake.
As we can see, the area is dotted with dots of various shapes and colors. These represent all the main earthquakes in the area in recent decades. The darker balls represent the seismes with deeper hypocenter, while the clearer ones with a more superficial hypocenter. The size of the dots is instead proportional to the magnitude. The bigger they are, the higher the magnitude.
If we look even more carefully, we can see how these earthquakes are not put at random, but they are all aligned along this black line. This symbolizes the limit between two busty plaques: the peaceful and the North American one. More specifically it is subduction of the peaceful plaque below the North American one. Subduction is that phenomenon that occurs when a tectonic plaque flows under another. This scrolling can create complex fault systems and large accumulations of energy which, when it is released, generates Very strong SISMI.
But it is not over, because subduction is one of the phenomena that can also give life to volcanoes, because the plate that descends warms up to such an extent from merge, go back, and give life to Volcanic arches. In this regard, now I also show you another image.
This is thePacific Ocean seen to the macoscalaand all this red band you see is the so -called Pacific fire belt. It is the area of the planet where there are more volcanoes and more earthquakes in the world. And coincidentally, the earthquake 8.8 earthquake is located just along this band. But it’s not over! If we look at the 5 strongest earthquakes ever recorded in history, they are all found in this huge area. And the 5th of these occurred in turn in Kamchatka in 1952 with a magnitude of 9.0.
