Why the earthquake in Crete today did so little damage (and no casualties) – Corriere.it

Why the earthquake in Crete today did so little damage (and no casualties) – Corriere.it
Why the earthquake in Crete today did so little damage (and no casualties) – Corriere.it

The shock was more intense than the one that hit Amatrice, but the characteristics (and effects) were very different

At 11.24 (Italian time) on Tuesday 12 October, off the far south-eastern tip of Chalk, happened an earthquake with a magnitude of 6.3 located at a depth of 9 kilometers.

Fortunately no victims were recorded e there was little damage: in the village of Xirokambos the wall of a church partially collapsed and there have been some landslides in the area. To have a comparison, the Amatrice earthquake of 24 August 2016 was of magnitude 6.0 at a depth of 8 kilometers: the victims were 303, the injured almost 400. Amatrice, Accumuli, Arquata del Tronto and other towns were destroyed, the displaced were numbered in the tens of thousands.

What causes this difference?

The differences
Not all earthquakes are the same, even if they have the same magnitude. This depends on many factors: the depth (the more a superficial earthquake is, the more damage is nearby; the deeper, the more you can feel it from a distance); the proximity of inhabited centers (in the Apennines the epicenter was practically under the villages, in Crete the epicenter was in the sea tens of kilometers from the coast, which is also sparsely populated); the presence of anti-seismic construction.

A decisive factor for the seismic and tectonic conformation of the area affected by the earthquake, the type of rocks, the presence of other active faults and superficial deposits of loose sand immediately below the buildings.

Another important factor where villages arise: in flat areas or on top of the hills, where seismic waves can be amplified.

Precedents
Tuesday in Crete was the strongest earthquake in 35 years in a radius of 30 kilometers. A little further west, on the mainland, on September 27th there was a quake with a magnitude of 5.8-6.0 with one victim, 36 injured and damage to some buildings, at the end of a seismic sequence that began four months earlier.

Crete rises close to where the African plate in its northward movement slips under (subduce, in geological jargon) that of the Aegean Sea (European), the contact area highlighted by the Hellenic Trench. The associated movements produce very intense and destructive earthquakes.

A 2009 study states that earthquakes up to magnitude 6.7 can occur in the eastern area of ​​Crete with a return period of around 900 years.

October 12, 2021 (change October 12, 2021 | 17:50)

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