More than 4,800 people were killed and thousands injured by a massive earthquake that struck southeastern Turkey, near the Syrian border, early Monday morning.
The quake, which struck near the city of Gaziantep, was closely followed by numerous aftershocks, including one that was nearly as large as the first.
Why was it so deadly?
It was a large quake – registered as 7.8, classified as “major” on the official magnitude scale. It ruptured along about 100 km (62 mi) of the fault line, causing extensive damage to buildings near the fault.
Professor Joanna Faure Walker, Director of the Institute for Disaster and Risk Reduction at University College London, said: “Of the deadliest earthquakes in any given year, only two in the last 10 years have been of equivalent magnitude, and four in the previous 10 years.”
But it’s not just the power of the tremor that causes devastation.
This event occurred in the early morning hours, when people were inside and sleeping.
The robustness of the buildings is also a factor.
Dr Carmen Solana, Lecturer in Volcanology and Risk Communication at the University of Portsmouth, says: “Unfortunately, resilient infrastructure is patchy in southern Turkey and especially Syria, so saving lives now largely depends on the response The next 24 hours are crucial to finding survivors.” After 48 hours, the number of survivors drops tremendously.”
This was a region where there had been no major earthquake for over 200 years and no warning signs, so the level of preparedness would be lower than for a region more used to dealing with tremors.
What caused the earthquake?
The Earth’s crust is made up of separate parts, called plates, that nestle next to each other.
These plates often try to move, but the friction of rubbing against a neighboring plate prevents it. But sometimes the pressure builds until a plate suddenly jolts, causing the surface to move.
In this case, it was the Arabian plate moving north and colliding with the Anatolian plate.
The friction of the plates has been responsible for very damaging earthquakes in the past.
On August 13, 1822, it triggered a magnitude 7.4 earthquake, significantly smaller than the 7.8 recorded on Monday.
Even so, the 19th-century earthquake caused immense damage to cities in the area, with 7,000 deaths recorded in the city of Aleppo alone. Damaging aftershocks continued for almost a year.
There have already been several aftershocks after the current quake, and scientists expect it to follow the same trend as the previous big quake in the region.
How are earthquakes measured?
They are measured on a scale called the Moment Magnitude (Mw) Scale. This has replaced the better-known Richter scale, now considered obsolete and less accurate.
The number attributed to an earthquake represents a combination of the distance the fault line has moved and the force that moved it.
A tremor of 2.5 or less is usually not felt, but can be detected with instruments. Tremors of up to five are felt and cause minor damage. The 7.8 earthquake in Turkey is classified as major and usually causes serious damage, as has happened in this case.
Anything above 8 causes catastrophic damage and can totally destroy communities at its center.
How does this compare to other large earthquakes?
The earthquake off the coast of Japan in 2011 registered as magnitude 9 and caused widespread damage to the land and triggered a tsunami, which led to a major nuclear plant accident along the coast.
The largest earthquake in history was 9.5 registered in Chile in 1960.
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