In the early hours of Monday, a massive earthquake struck southeast Turkey near the Syrian border, causing more than 1,700 deaths and thousands of injuries.
The quake that occurred near the city of Gaziantep was quickly followed by a second tremor of comparable magnitude.
Why was it so deadly?
It was a major quake. The magnitude of the one near Gaziantep was estimated to be 7.8, making it "major" on the official scale. Its center was relatively shallow at approximately 18 kilometers (11 miles), causing severe damage to structures.
Prof. Joanna Faure Walker, director of the Institute for Risk and Disaster Reduction at University College London, stated, "Only two of the deadliest earthquakes in any given year have been of comparable magnitude in the last ten years, compared to four in the previous ten."
But the magnitude of the earthquake is not the only factor that causes destruction.
This incident occurred during the early morning hours, when people were sleeping inside.
The durability of the structures is also a factor.
Professor of volcanology and risk communication at the University of Portsmouth, Dr. Carmen Solana, states: "Unfortunately, the resiliency of the infrastructure in southern Turkey and Syria, particularly, is lacking, so saving lives now depends primarily on response. The next twenty-four hours are crucial for locating survivors. After 48 hours, the number of survivors is drastically reduced."
This region had not experienced a major earthquake or any warning signs for more than 200 years, so the level of preparedness would be lower than in a region that was more accustomed to dealing with earthquakes.
What caused the earthquake?
The Earth's crust is composed of separate pieces, known as plates, that fit snugly together.
These plates frequently attempt to move, but are prevented by the friction created when they rub against one another. Occasionally, however, the pressure builds until one plate jerks across, causing the surface to shift.
In this instance, it was the Arabian plate grinding against the Anatolian plate as it moved northward.
In the past, extremely destructive earthquakes have been caused by plate friction.
It caused a 7.4 magnitude earthquake on August 13, 1822, significantly less than the 7.8 magnitude recorded on Monday.
Even so, the earthquake of the nineteenth century caused extensive damage to the region's towns, with 7,000 deaths recorded in Aleppo alone. Nearly a year of damaging aftershocks continued to occur.
Numerous aftershocks have already followed the current earthquake, and scientists anticipate that it will follow the same pattern as the previous major earthquake in the region.
How are earthquakes measured?
On a scale called the moment magnitude scale, they are measured.
A tremor of magnitude 2.5 or less is typically inaudible but can be detected by instruments. Up to five magnitude earthquakes are felt and cause minor damage. The 7.8 magnitude earthquake in Turkey is classified as a major quake and has caused extensive damage, as is typical.
Any number greater than eight causes catastrophic damage and can obliterate communities at their core.
In 2011, a magnitude 9 earthquake off the coast of Japan caused widespread damage to the land and a series of enormous tidal waves, one of which caused a major accident at a nuclear plant along the coast.
In 1960, a magnitude 9.0 earthquake was recorded in Chile.