The quake killed thousands in Turkey and Syria. This is what happened

A major 7.8 magnitude earthquake followed by another strong quake devastated wide swaths of Turkey and Syria Monday, killing thousands of people.

Here's a timeline of how it happened:

Initial quake

At about 8:30 p.m. ET on Sunday, the U.S.Geological Survey (USGS) registered a 7.8 magnitude earthquakeat a depth of 18 kilometres andcentred in southern Turkey, near the northern border of Syria.

Residentsjolted out of sleep by the pre-dawn quake rushed outside in the rain and snow to escape falling debris, while those who were trapped cried for help.

Researchers said theearthquake was a strike-slip quake, where two tectonic plates slide past each other horizontally.

The epicentre was near Gaziantep, a major city and provincial capital in Turkey. The affected regions were also home to vulnerable buildings, said Kishor Jaiswal, a USGS structural engineer.

While new buildings in cities like Istanbul were designed with modern earthquake standards in mind,this area of southern Turkey has many older high-rise buildings, Jaiswal said. Rapid construction in Syria plus years of war may have also left structures vulnerable, researchers said.

Officials reportedthousands of buildings collapsed in the wake of the earthquake. They included "pancake" collapses, where upper floors of a building fall straight down onto the lower floors a sign that the buildings couldn't absorb the shaking, Jaiswal said.

Among thedamaged buildings wasGaziantep's most famed landmark, its historic castle perched atop a hill in the centre of the city.

Parts of the fortress'swalls and watch towers were levelled and other parts heavily damaged, images from the city showed.

2nd quake

Another strong quake magnitude 7.5 hit Turkey nine hours after the main jolt. Though scientists were studying whether that was an aftershock, they agreed that the two quakes are related.

"More aftershocks are certainly expected, given the size of the main shock," Hatem said. "We expect aftershocks to continue in the coming days, weeks and months."

The second jolt in the afternoon caused a multi-storey apartment building to topple face-forward onto the street in the Turkish city of Sanliurfa. The structure disintegrated into rubble and raised a cloud of dust as bystanders screamed, according to video of the scene.

Aftershocks

Many aftershocks rocked the two countries since the initial quake. In the first 11 hours, the region had felt 13 significant aftershocks with a magnitude of at least 5, said Alex Hatem, a USGS research geologist.

Rescues hindered

After night fell, workers were still sawing away slabs and pulling out bodies as desperate families waited for news on trapped loved ones.

Rescue efforts have been hampered by freezing temperatures and traffic jams from residents trying to leave quake-stricken areas.

In Turkey's Gaziantep, a provincial capital about 33 kilometres from the epicentre, people took refuge in shopping malls, stadiums and community centres. Mosques around the region were opened to provide shelter.

"This is the awful level of devastation and destruction that we would expect to see" when a strong quake hits a region with buildings that have not been shored up, said Ilan Kelman, an expert in disasters and health at University College London.

WATCH | What lies ahead for Turkey:

Whats ahead for Turkey after massive earthquake

2 years ago

Duration 3:24

Meteorologist and seismologist Johanna Wagstaffe talks about the aftershocks that are happening and will continue to happen in Turkey, a country prone to seismic activity.

'Almost all of Turkey is really seismically active '

The quake occurred in a seismically active area known as the East Anatolian fault zone, which has produced damaging earthquakes in the past.

"Almost all of Turkey is really seismically active," Sandvol said. "This is not something new to the country."

Turkey was struck by another major earthquake in January 2020 a magnitude 6.7 that caused significant damage in the eastern part of the country. In 1999, a 7.4 magnitude quake struck near Istanbul and killed an estimated 18,000 people.