(ORDO NEWS) — On May 22, 1960, a devastating earthquake occurred in southern Chile. For 10 minutes, the ground shook so much that people could not stand on their feet.
Cracks formed on the roads, houses collapsed. The Vildivia earthquake had a magnitude of 9.5, the strongest in recorded history. But can such shocks be even stronger?
According to geologists, the answer to this question is yes. But the probability of earthquakes with a magnitude higher than 9.5 is unlikely.
For this to happen, a very long and very deep rupture of a huge fragment of the earth’s crust must occur.
As geologist Wendy Bohon said, most likely a magnitude 9.5 earthquake is the most powerful that can happen on Earth. A magnitude of 10 is highly unlikely.
“This idea is good for Hollywood, but thank heavens it’s not realistic on Earth,” she added.
Magnitude is a measure of the amount of energy released during an earthquake.
It can differ from how an earthquake is felt on the surface, since in this case the force depends on the distance to the epicenter and the state of the earth.
The same earthquake can be felt differently by someone standing on loose soil or sand and by someone standing on a hard surface.
The magnitude of the earthquake depends on the total area of the rupture. And it, in turn, depends on how deep the fault goes into the earth’s crust, and the length of the broken segment horizontally.
There are physical limits to how large an area can collapse. The deepest faults are found in subduction zones, where one tectonic plate pushes against another.
Although earthquakes can sometimes occur as deep as 800 kilometers below the Earth’s surface, according to the US Geological Survey, most deep earthquakes do not cause strong tremors at the surface.
The most dangerous for people are those located in the upper tens of kilometers of the earth’s crust.
According to Heidi Houston, an earthquake geologist at the University of Southern California, the faults that can cause the most destructive earthquakes are inclined faults in subduction zones.
They are called slumping because they are at an angle, rather than vertical, and have the largest areas of rock that can jam into each other, building up stress and then finally collapsing.
There are also physical limits to the size of a segment that can “break”. Even faults in subduction zones do not collapse immediately.
Another factor that affects magnitude is how much the fault slips or shifts. As a rule, smaller areas of subsidence move a shorter distance than larger ones.
That is, in a magnitude 5 earthquake, the rock can slip a few centimeters – a distance that is unlikely to destroy the ground above – in a magnitude 9 earthquake, the fault can move a distance of about 20 meters or more.
The 1960 earthquake in Chile actually increased the area of the country because of how the land stretched.
According to scientists, the difference between a magnitude 8 and a magnitude 9 earthquake in terms of energy released is much greater than the difference between a magnitude 5 and a magnitude 6.
To increase the magnitude of an earthquake from 9.5 to 9.6 requires a much larger area of destruction fault than the increase in magnitude from 5.5 to 5.6.
That is, the earthquake in Chile was almost twice as powerful as the 9.2-magnitude earthquake in Alaska next to it in the scale of records.
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