Thousands of people have died after a massive earthquake struck Turkey and Syria on Monday.
A search and rescue operation is underway, with teams of specialists arriving from around the world.
However, people in some hard-hit areas say rescue efforts have been slow. Some have had to dig with their bare hands to find their relatives.
How do you start a search and rescue operation?
When rescuers first arrive at the scene of an earthquake, they assess which collapsed buildings are most likely to contain trapped people.
They do this by searching for “voids”: spaces under large concrete beams or stairwells where survivors can be found.
The possibility of a building collapsing further must also be considered, as should other hazards such as gas leaks, flooding, and hazardous items such as asbestos on roofs.
As rescuers try to reach the survivors, support workers watch the building move and listen for strange sounds.
Buildings that have completely collapsed are usually the last to be searched for, because the chance of finding survivors is very slim.
The work of the rescue teams is coordinated by an agency, usually the United Nations (UN) and the host country. Rescuers are specially trained and work in pairs or larger teams, while local people are often involved as well.
What rescue equipment is needed?
To move the rubble, rescue teams use heavy machinery, including bulldozers and hydraulic jacks.
Bulldozers can push aside large slabs of concrete on the outside of buildings, allowing rescuers a view of the people trapped inside.
Video equipment at the end of the flexible poles can be passed through the gaps to help locate survivors.
Specialized sound equipment can detect the slightest noise with an accuracy of a few meters. Silence is required at the site as a member of the rescue team knocks three times and waits to hear a response.
Carbon dioxide detectors can be used to find unconscious survivors. They work best in confined spaces where they detect the highest concentration of CO2 in the air exhaled by those who are still breathing.
Thermal imaging equipment can be used to locate people who are not directly in a rescuer’s line of sight, as their body heat can heat the debris around them.
What do rescue dogs do?
Using their sense of smell, specially trained dogs can detect signs of life where human rescuers cannot.
Dogs can also cover large areas quickly, speeding up the search and rescue process.
Do people need to use their own hands?
Once the large slabs and structures are removed, rescue teams use their hands and small tools such as hammers, picks, and shovels, as well as chainsaws, disc cutters, and rebar cutters, which can be used to tackle the rebar. metal in reinforced concrete.
They have protective gear, including hard hats and gloves to protect their hands while removing sharp debris.
However, in some areas of Turkey, where rescue efforts have been slow and machinery unavailable, local people have been digging through the wet and frozen rubble with their bare hands.
Bedia Gucum, a restaurant owner in Adana, southern Turkey, told the BBC: “We need strong work gloves to move that rubble by hand. Because once they hear there’s someone alive there, all the heavy machinery it stops and they have to dig with their bare hands, and that is beyond human capabilities.
“You need hands on site, and you need gloves for them.”
How is the end time of an operation decided?
This decision is made between the UN coordinating agency and the central and local government of the host country.
Search and rescue attempts are generally called off five to seven days after a disaster, once no one has been found alive for a day or two.
However, people have been known to be rescued alive beyond this point.
In 2010, a man was found alive after 27 days trapped under rubble following an earthquake in Haiti.
In 2013, a woman was rescued from the ruins of a factory building in Bangladesh, 17 days after it collapsed.