The temblor is Taiwan's strongest in 25 years. Some buildings tilted at precarious angles in the mountainous county of Hualien, near the epicentre of the quake, which struck just offshore about 8am on Wednesday (local time) and triggered massive landslides.
Buildings also shook violently in capital Taipei, but damage and disruption there was minimal.
Taiwan's fire department said on Thursday the number of injuries had reached 1050, putting the total number of missing at 52. About two dozen of almost 50 hotel workers on their way to a resort in Taroko National Park had been located.
The fire department said the group was trapped on the cross-island highway which traverses the gorge connecting Hualien with Taiwan's west coast and is a popular tourist destination.
It showed drone footage of some of the hotel workers, along with other people, waving from the side of a road, with the crushed back part of a minibus also clearly visible. Another group of 26 workers had also been found, it added.
On Thursday morning, a helicopter rescued six people who had been trapped in a mining area, the fire department said.
Fire authorities said they had already evacuated some 70 people trapped in tunnels near Hualien city, including two Germans.
On a highway through the mountains, huge boulders from a landslide were strewn across the road. The Fire Bureau of Taichung City Government said it rescued a man in his 50s who was unconscious in a truck.
The power of the quake was captured live as news anchors delivered their bulletins, steadying themselves against giant screens as their sets swayed and lighting rigs rocked back and forth overhead.
It hit at a depth of 15.5km, as people were headed for work and school, setting off a tsunami warning for southern Japan and the Philippines that was later lifted.
"At present the most important thing, the top priority, is to rescue people," said President-elect Lai Ching-te, speaking outside one of the collapsed buildings in Hualien.
The railway line to Hualien re-opened ahead of schedule on Thursday, although one rural station north of Hualien city remains closed due to damage, the railway administration said.
'WE ARE SO NERVOUS'
In Hualien city, where people who had been trapped in buildings have all been rescued, some people slept outdoors overnight as dozens of aftershocks rocked the region.
A lady, 52, who gave her family name as Yu, said she checked herself into a tent on a sports ground being used for temporary shelter late on Wednesday night because she was too scared to sleep in her apartment, which she described as "a mess".
"The aftershocks were terrifying. It's nonstop. I do not dare to sleep in the house," she said.
"We worry the house could collapse anytime. We thought we had already experienced it once in Hualien and it would not hit us again, because God has to be fair," she said.
"We are frightened. We are so nervous."
A woman who runs bed-and-breakfast accommodation in Hualien city said she scrambled to calm her guests who were scared by the quake.
"This is the biggest earthquake I have ever experienced," said the woman, who asked to be identified only by her family name, Chan.
The city's mayor, Hsu Chen-Wei, said all residents and businesses in buildings that were in a dangerous state had been evacuated and demolition work was beginning on four.
Taiwan's official central news agency said the quake was the biggest since one of magnitude 7.6 in 1999 that killed about 2400 people and damaged or destroyed 50,000 buildings.
Local weather officials ranked Wednesday's quake in Hualien as "Upper 6", or the second-highest level of intensity on a scale ranging from 1 to 7.
Such quakes collapse walls unless they are made of reinforced concrete blocks, while people cannot stand upright and must crawl in order to move, experts say.
FIGHTER JETS
The White House said the United States stood ready to provide any assistance necessary.
Taiwan's air force said six F-16 fighter jets had been slightly damaged at a major base in the city from which jets are often scrambled to see off incursions by China's air force, but the aircraft were expected to return to service very soon.
In Japan, the weather agency put the quake's magnitude at 7.7, saying several small tsunami waves reached parts of the southern prefecture of Okinawa, while downgrading its tsunami warning to an advisory. In the Philippines, seismology officials warned coastal residents in several provinces to move to higher ground.
Chinese state media said the quake was felt in the southeastern province of Fujian, while a Reuters witness said it was also felt in the commercial hub of Shanghai.
CHIP SUPPLIES
Aftershocks could still be felt in Taipei, with more than 50 recorded, weather officials said.
Most power had been restored after the quake, electricity utility Taipower said, with the island's two nuclear power stations unaffected.
A major supplier of chips to Apple and Nvidia, Taiwan Semiconductor Manufacturing, said it had evacuated some fabrication plants and safety systems were operating normally.
It said later its workers were safe and had returned to their workplaces shortly after the earthquake. It said impacted facilities were expected to resume production during the night.
