Earthquakes are always unpredictable anywhere in the world, but there are areas that are geologically prone to them and are therefore well prepared to deal with earthquakes. None of these circumstances occurred in the region of Morocco that was devastated last morning by an earthquake that also had an unusual intensity. This cocktail of factors explains the high number of deaths and the destruction that the episode has left behind.
These are the main keys to understanding what has happened in Morocco.
The earthquake broke out at 11:11 p.m. on Friday in Morocco (one hour more in mainland Spain) with a magnitude of 6.8 according to calculations by the National Geographic Institute (IGN) and the United States Geological Survey (USGS), reference for these situations. The epicenter has been located in the town of Iguil63 kilometers southwest of Marrakech, with the province of Al Haouz as the most affected region. However, up to six provinces have been shaken by the earthquake, with collapsed buildings. Just 20 minutes after the main earthquake, an aftershock of magnitude 4.9 occurred, followed by another 25 aftershocks of magnitudes between 3 and 4.
Is it common in Morocco?
It is the strongest earthquake that the country has suffered since records have been kept (at least since 1900) and surpasses the earthquake of magnitude 6.4 that shook northern Morocco in 2004 and caused more than 600 deaths. The deadliest earthquake occurred in Agadir in 1960, which with a magnitude of 5.8, killed more than 12,000 people. That is to say, although this has not been the earthquake with the most victims, it has been the one with higher intensity. “An earthquake could be expected there, but not so strong, at most magnitude 5,” the IGN seismologist explained to EFE. Carlos Gonzalez. The area has mapped faults, but with lower and less frequent seismicity than in the north of the country, near the border between the African and Eurasian plates.
Why has it been so powerful?
Apparently, the cause could be a thrust fault called South Atlas, which is mapped but was not expected to reach magnitudes of 6.4. And the earthquake occurred in the vicinity of the Atlas mountain range, a faulty system generated as a result of the collision of the aforementioned plates. The energy that is released as a consequence of these geological frictions causes the earth tremor. Another key factor has been shallow depth of the epicenter, 8.5 kilometers. At greater depths, the waves become attenuated and the effects are smaller. The more superficial, the greater the damage. This unusual power also explains why the earthquake was felt in many Spanish provinces.
Why has it been so destructive?
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In addition to depth, the strength of buildings is the other crucial factor. As these are rural regions and unaccustomed to strong earthquakes, the buildings It is not prepared to withstand tremors of such intensity. According to the USGS, vulnerable buildings predominate in the area, such as those in adobe blocks and bricks unarmed with mud construction. Older parts of cities are also more likely to be damaged than taller buildings in modern areas, as has happened in Marrakesh. And the fact that the earthquake took place at nightwhen many people are at home, and even sleeping, it aggravates personal injuries.
What force has he released?
The two parameters used to measure earthquakes are magnitude and intensity. The magnitude, which expresses the net energy that is released, has been 6.8. The intensity, which measures the social and environmental impact of the earthquake (deaths, injuries, collapsed buildings…), has been VIII (destructive) and IX (very destructive), depending on the area. This scale goes from I (very weak) to XII (catastrophic) and does not depend on the magnitude, but on the effects caused by the tremor. For example, earthquakes Türkiye and Syria last February (magnitude 7.8 and with 50,000 deaths) were also intensity IX, while the earthquake in Lorca (Murcia) in 2011 (magnitude 5.1 and 9 deaths) was intensity VII.