Why the earthquake in Turkey and Syria is one of the deadliest of this century?

Look how the serious fire in a port in Turkey looks from the sky 1:40

(CNN) --

The devastating earthquake that struck Turkey and Syria on Monday has killed more than 7,000 people and injured tens of thousands.

Thousands of buildings have collapsed in the two countries and aid agencies are warning of "catastrophic" repercussions in northwestern Syria, where millions of vulnerable and displaced people already depend on humanitarian aid.

• Latest earthquake news in Turkey and Syria: more than 7,000 dead and tens of thousands injured

The international community is offering assistance in search and recovery operations.

Meanwhile, agencies have warned that the fatalities from the catastrophe could rise sharply.

Here's what we know about the quake and why it was so deadly.

Where did the earthquake occur?

One of the most powerful earthquakes in the Middle East in a century jolted residents from their slumber early Monday morning, around 4 a.m. local time.

The quake struck 23 kilometers east of Nurdagi, in Turkey's Gaziantep province, at a depth of 24.1 kilometers, the United States Geological Survey (USGS) reported.

A series of aftershocks reverberated across the Middle East in the hours immediately following the initial incident.

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A magnitude 6.7 aftershock struck 11 minutes after the first quake, but the largest tremor, magnitude 7.5, struck about nine hours later, at 1:24 p.m., according to the USGS.

The magnitude 7.5 aftershock, which struck about 95 kilometers north of the initial quake, is the strongest of more than 100 that have been recorded so far.

Rescue teams battle against time and the elements to pull survivors out of the rubble on both sides of the border.

More than 5,700 buildings have collapsed in Turkey, according to the country's disaster agency.

Monday's earthquake was also one of the strongest to hit Turkey in the last century: a 7.8-magnitude quake struck the east of the country in 1939, killing more than 30,000 people, according to the USGS.

why do earthquakes happen?

Earthquakes occur on every continent in the world, from the highest peaks of the Himalayas to the lowest valleys, such as the Dead Sea, passing through the coldest regions of Antarctica.

However, the distribution of these earthquakes is not random.

The USGS describes an earthquake as "the shaking of the ground caused by a sudden slip on a fault. Stresses in the outer layer of the earth push the sides of the fault against each other. The stress builds and rocks slide suddenly, releasing energy in waves that travel through the Earth's crust and cause the shaking we feel during an earthquake.

Earthquakes are measured with seismographs, which record the seismic waves that travel through the Earth after a telluric movement.

Scientists used the Richter scale for many years, but now largely follow the modified Mercalli intensity scale, which the US Geological Survey says is a more accurate measure of magnitude, according to the USGS.

The Richter scale measures magnitude, while the MMI scale measures intensity.

Aerial footage of earthquake destruction in Turkey and Syria 0:50

How strong is a magnitude 7.8 earthquake?

The power of an earthquake is known as magnitude.

The intensity of the shaking can vary depending on the local geography and topography and the depth of the earthquake.

On the magnitude scale, each increase of a whole number translates to 32 times more energy.

This time, the shocks of the 7.8 magnitude earthquake in southern Turkey could be felt as far as Israel and Lebanon, hundreds of kilometers away.

Turkey is no stranger to strong earthquakes, as it is situated along tectonic plate boundaries.

Seven earthquakes of magnitude 7.0 or higher have shaken the country in the last 25 years, but Monday's was one of the most powerful.

It is also the strongest earthquake to strike anywhere in the world since a magnitude 8.1 tremor struck a region near the South Sandwich Islands in the southern Atlantic Ocean in 2021, although the remote location of that incident did little damage.

Karl Lang, an assistant professor in Georgia Tech University's School of Earth and Atmospheric Sciences, told CNN that the area affected by Monday's quake is prone to seismic activity.

"It's a seismogenic zone. It's a very large fault zone, but this is a bigger earthquake than they've experienced at any time in recent memory," Lang said.

"The magnitude of the shaking felt at the surface depends both on the amount of energy released, the size of the earthquake, and the distance that energy is released below the surface. So if you're very close to the surface If it's a shallow earthquake, it can be very dangerous."

Why are there so many earthquakes in Turkey?

CNN meteorologist and severe weather expert Chad Myers said: "We always talk about the epicenter, but in this case we should talk about the epiline."

Two huge tectonic plates, the Arabian and the Eurasian, lie under the southeastern provinces of Turkey.

Along this fault, "the land slid about 100 miles from one side to the other," Myers continued.

Seismologists refer to this phenomenon as "bump slip," "when the plates touch and suddenly slide sideways," Myers explains.

This is not like the Ring of Fire, which runs along the west coast of the United States.

In this area, earthquakes and tsunamis are usually due to subduction, that is, the sliding of one plate under another.

But in a "bump slide," the plates move horizontally, rather than vertically.

"That's important because the builds don't want to go back and forth. And then the secondary waves start going back and forth as well," Myers adds.

Due to the nature of this seismic event, aftershocks could last "weeks and months," according to CNN meteorologist Karen Maginnis.

How does this earthquake compare globally?

Compared to other large earthquakes around the world, the 2011 Japan earthquake and tsunami, which killed or disappeared more than 22,000 people, registered a magnitude of 9.1.

That incident left widespread destruction in its wake after walls of water engulfed entire cities, washed homes onto highways and sparked the country's worst nuclear disaster on record.

A year earlier, in 2010, an estimated magnitude 7.0 earthquake in Haiti caused between 220,000 and 300,000 deaths.

Another 300,000 people were injured and millions were displaced.

In 2004, a magnitude 9.1 earthquake struck off the coast of Sumatra, Indonesia, triggering a tsunami that left 227,898 dead or missing.

The strongest earthquake on record was a magnitude 9.5 in Chile in 1960, according to the USGS.

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  The answer is not as simple as it might seem.

Why was it so lethal?

Several factors have contributed to making this earthquake so deadly.

One of them is the time of day it occurred.

As the quake struck at dawn, many people were in their beds when it struck, and are now trapped under the rubble of their homes.

Additionally, with a cold and wet weather system moving through the region, poor conditions have made rescue and recovery efforts on both sides of the border significantly more difficult.

Temperatures are already very low, but this Wednesday it is expected to drop several degrees below zero.

A zone of low pressures currently hangs over Turkey and Syria.

According to Britley Ritz, CNN's chief meteorologist, when it moves away, it will bring "much cooler air" from central Turkey.

A temperature of -4°C is forecast in Gaziantep and -2°C in Aleppo this Wednesday morning.

For Thursday, the forecast drops further, down to -6 and -4 °C respectively.

The conditions have already made it difficult for aid teams to access the affected area, Turkish Health Minister Fahrettin Koca said, adding that the helicopters were unable to take off on Monday due to bad weather.

Despite the conditions, the authorities have asked residents to leave the buildings for their own safety in view of the possibility of further aftershocks.

With so much damage in both countries, many are beginning to wonder what role the local building infrastructure might have played in the tragedy.

Kishor Jaiswal, a structural engineer with the USGS, told CNN on Tuesday that Turkey has suffered major earthquakes in the past, such as the one in 1999, which shook the southwest of the country and killed more than 14,000 people.

According to Jaiswal, many areas in Turkey have been designated as high-risk seismic zones, and as such, the region's building regulations state that construction projects must withstand such events and, in most cases, prevent landslides. catastrophic, if done correctly.

But not all the buildings have been built according to modern Turkish seismic standards, says Jaiswal.

Poor design and construction, especially in older buildings, render many unable to withstand the severity of shaking.

"If these structures are not designed for the seismic intensity that they may face in their design life, these structures may not perform well," Jaiswal said.

He also warned that many of the structures that remain standing could be "significantly weakened by those two strong earthquakes that we've already seen. There's still a small chance of an aftershock strong enough to topple those deteriorating structures. So During this aftershock activity, people must be very careful when accessing these weakened structures for these rescue efforts."

How can you help

Hundreds of thousands of Syrian refugees, already displaced by the civil war in their country of origin, are settled in the regions of Turkey most affected by the earthquake on Monday.

Turkey hosts more than 3.6 million Syrian refugees, according to Human Rights Watch data.

Many of these refugees are settled along the Turkish-Syrian border.

The provinces of Hatay, Gaziantep and Sanliurfa each host more than 300,000 Syrians, according to data from the United Nations High Commissioner for Refugees.

• These are the countries that promised help to Turkey and Syria to deal with the earthquake

Other neighboring provinces are also home to hundreds of thousands of other refugees, who have fled their country of origin since the start of the Syrian conflict in 2011.

Following the disaster, the International Federation of Red Cross and Red Crescent Societies (IFRC) said it was "launching immediate cash assistance" from its Emergency Fund for Disaster Response to help to relief efforts in both countries.

Natural disastersTurkey