Venezuela lies in a seismically active zone where two tectonic plates, the Caribbean and the South American, meet.

According to the US Geological Survey, the second and larger of the two quakes today occurred as a result of "shallow strike-slip faulting" near the boundary of these plates.

This is when faults, or fractures between the plates, move horizontally. An earthquake is caused when this movement happens quickly.

"While commonly plotted as points on maps, earthquakes of this size are more appropriately described as slip over a larger fault area," USGS reports.

The pair of quakes today "likely indicates a complex, rupture interaction process", the organisation says.

Aftershocks, including "some potentially with strong shaking" are still possible, it adds.

Image source, Getty Images

"The two major earthquakes that just hit the great people of Venezuela are both massive in scale and have left a devastating number of deaths," US President Donald Trump has written in a post on Truth Social.

"The U.S.A. stands ready, willing, and able to help!"

Trump says he has "instructed all agencies of our government to get ready to move quickly.

"We will be there for our new and great friends. Early reports are not good!!!" There have so far been no official public reports on the number of casualties.

Valentina Oropeza
BBC Mundo

My sister Veronica sent me an audio message on WhatsApp yesterday evening: "The house just shook horribly, it's still shaking."

Living in the US, I had not yet caught up with what was happening in Caracas. For the next two hours, Veronica did not respond to my calls – and neither did our mother, who was with her.

I soon learned about the earthquake through a chat group with journalists in Caracas. Then a friend sent me a clip of a building in Los Palos Grandes that had disintegrated like a cookie.

I recognised it immediately – It was just a few metres from where Veronica and mum were.

By this time, my phone was beeping continuously with updates of damage in the area. I was so worried.

It wasn't until two hours later that I heard from Veronica again, when she regained internet connection.

"Sister, I thought we were going to die," she said before hanging up. She'll return home tomorrow to see if she still has a place to live.

Image source, Getty Images

The US will dispatch search and rescue teams and medical and humanitarian supplies to Venezuela, says Jeremy Lewin, Under Secretary of State for Foreign Assistance.

The State Department has a disaster assistance team that's working with partners in the interim Venezuelan government, he says.

Countries in Latin America have also offered assistance.

El Salvador president Nayib Bukele says his country has prepared 50 tonnes of equipment and supplies, as well as 300 rescuers who are "ready to depart for Caracas".

Ecuador, too, has arranged aid to be sent immediately to Venezuela, says its President Daniel Noboa Azin.

Meanwhile, Brazilian President Luiz Inácio Lula da Silva has said his country will assess what measures of assistance it can adopt to support its "sister nation".

Mexico's Secretary of Foreign Affairs Roberto Velasco Álvarez also offered Venezuela "all the solidarity and support it may require".

Vanessa Buschschlüter
Latin America and Caribbean editor

Acting President Delcy Rodríguez told Venezuelans in an address on state TV that train and metro services would be halted for the time being.

She also said that classes would be suspended for the remainder of the week.

Maiquetía international airport, which is located on the outskirts of Caracas, has also been closed after parts of the ceiling collapsed.

More than 20 aftershocks have rattled Venezuela since the first earthquakes hit on Wednesday, AFP news agency reported, citing the president's office.

The hardest hit areas are along the country's northern coast, including La Guaira, Aragua, Carabobo and Falcón.

Photographs taken in the hours since the tremors struck show residents gathered along the streets of Venezuela's capital, after their homes shook and the power went out.

Some hug their siblings and pets, while rescuers sift through debris for those trapped.

Authorities fear high casualties, but the full extent of damage is still unknown.

Image source, Getty Images

Image source, Getty Images

Image source, EPA

Image source, EPA

Image source, Getty Images

BBC Mundo contributor Nicole Kolster said earlier that people could be heard calling for help from under the rubble of a collapsed building.

“‘Ask for help. We’re here,’ is what you can hear,” she said.

After the quake, others were "still outside waiting for safety in case there’s an aftershock,” Kolster added.

“The recommendation is not to go back up into the building,” she explained.

Maria Elise, a local from the Caracas suburb of Palos Grandes, described how her apartment "has some cracked walls. There are fallen utility poles, we have no electricity, no signal."

Footage from the ground, captured by BBC reporter Vanessa Silva, shows rescuers searching for survivors under the debris of a collapsed multi-storey building in the north Caracas suburb of San Bernardino.

Unconfirmed reports suggest that at least one person has died in the neighbourhood.

Twin earthquakes have caused multiple buildings to collapse in the Venezuelan capital, and authorities fear there could be high casualties and extensive damage across the city.

Maiquetía airport, Venezuela's main international airport, has been closed due to "serious damage" from the earthquake, Rodríguez says.

Footage that emerged from the airport earlier showed people fleeing through its corridors and dust columns billowing down from its ceilings as the quakes hit.

Vanessa Buschschlüter
Latin America and Caribbean editor

Venezuela's acting President Delcy Rodríguez has just addressed the nation.

Flanked by Interior Minister Diosdado Cabello and her brother Jorge Rodríguez, who is the head of the National Assembly, she declared a state of emergency.

She also designated a general to oversee the emergency response.

Rodríguez has been leading the country on an interim basis since her predecessor, Nicolás Maduro, was seized by US forces in January and taken to New York to stand trial on drug-trafficking charges.

In her speech, she appealed above all for unity from the Venezuelan people.

She also gave her condolences to those who had lost loved ones in the quake, without giving numbers of fatalities.

Footage has emerged of people fleeing through the halls of Maiquetía airport as the quake hits, while trying to shield themselves from falling debris.

Vanessa Buschschlüter
Latin America and Caribbean editor

Image source, Getty Images

The mayor of Chacao, Gustavo Duque Saez, says there are at least two buildings in this municipality - which forms part of the greater metropolitan area of Caracas - which have completely collapsed.

He says that 18 people had been rescued alive and that more than 500 emergency workers were on site trying to pull out more residents.

"In Chacao, no one is alone, and we won't move from here until every resident is rescued."

He also urged locals trying to track down missing relatives to go to two main local squares - Plaza Altamira and Plaza Los Palos Grandes - where local officials have set up an emergency centre, where information is being collated and those affected are provided with water and shelter.

"Not only do we have two building which have collapsed but also a list of others whose structure has been compromised."

Image source, Getty Images

In a post on X, the US embassy in Caracas says it is "closely monitoring the aftermath" of the earthquake.

It urges people to "avoid damaged areas and do not enter damaged buildings".

In further guidance, it adds that people should monitor local media for updates and "seek secure shelter".

Further to Vanessa's video of the moment when the quake struck, the journalist has described to us the aftermath of the tremor.

The number of deaths and injuries is not yet known, she says, but she describes how her own neighbour broke her arm during the shaking.

"Oh God! Oh God!" exclaims BBC reporter Vanessa Silva as the earthquake hits her home in Caracas.

A chandelier - and the apartment itself - can be seen shaking while a rumbling is heard in the background.

Image source, Getty Images

If you're just joining us, here's a round-up of what's happened so far:

• Two powerful earthquakes struck Venezuela on Wednesday evening under a minute apart
• The first 7.2-magnitude quake was centred in San Felipe, in the state of Yaracuy
• It was followed by a stronger earthquake just 39 seconds later, with that one registering a 7.5 magnitude, the US Geological Survey says
• It's still unclear how many casualties there have been and what the extent of the damage will be
• The USGS says high casualties and extensive damage are probable with a 44% chance of more than 10,000 fatalities and a 30% chance of more than 100,000 following the second mainshock quake
• The shaking was felt in Caracas, where buildings have collapsed, petrol supplies have been cut off and people are calling for help under the rubble
• The interior minister has urged residents to leave their homes

Cracked glass and smashed food containers litter the floor of one Caracas resident's home.

Juan Arraez says this is the "heaviest quake I've felt in Venezuela".

“It’s the strongest quake I’ve ever felt in my life,” journalist and BBC Mundo contributor Nicole Kolster says.

She was on the 7th floor of an apartment building in Palos Grandes, central Caracas, when the earthquake began.

"I saw the windows moving and the only thing I could think to do was to get between the front door and a stone wall, which in my judgment is quite strong, to try to protect myself,” Kolster recounts.

She stayed there “for quite a while,” until she heard neighbours shouting for everyone to go down to the street.

"I thought the building was going to fall on top of me," she says.

Vanessa Buschschlüter
Latin America and Caribbean editor

Image source, Getty Images

The first quake struck at 18:04 local time (22:04 GMT) which would normally have been the height of the rush hour.

But 24 June is a national holiday in Venezuela, commemorating the 1821 Battle of Carabobo, a decisive victory by Venezuelan independence leader Simón Bolívar against the Spanish colonial power.

More people than usual would therefore have been at home than on a normal weekday.

Footage shared on social media showed residents rushing into the streets.

In one video two men can be seen trying to hold on to a swaying vitrine full of china, while items crash to the floor.

You can also get live updates on BBC News Mundo, our Spanish language website.