Aftershocks hit north-eastern Turkey yesterday as fears spread that they were a prelude to cataclysmic earthquakes in Istanbul.
Seismologists at the country's Kandilli observatory warned that a major fault system had been activated, and that it was a question of when, not if, the metropolis would be hit.
Freezing, homeless survivors of Friday's earthquake in Duzce said they would rather live in tents than accept shelter in Istanbul, 170 km to the west.
The discovery of an unbroken section of fault line beneath the Marmara sea, just south of the city made it more likely that the so-called Big One was on its way, said Mr Ahmet Isikara, the observatory's chief seismologist.
Istanbul, Turkey's cultural and economic heart, has 10 million inhabitants packed into often badly built blocks of flats.
Friday's quake made some of the city's blocks wobble like rubber, sending hundreds of people running into the street. They lit fires and spent the night out of doors.
A closer, more powerful quake could strike at any time, said Mr Isikara. "We have to live with this reality. One should ask how to minimise damage, instead of asking if there will be another quake.
"There is a seismic vacuum in the west," he said. The timing of the strike was impossible to predict and could be minutes, months or years away, he said.
Trucks laden with blankets, food, tents and building materials streamed across the Bosphorus to aid survivors of Friday's tremor, which devastated the province of Bolu, killing more than 380 people and injuring 2,000.
The seismologists' warning threw into doubt initial hopes of resettling the homeless in Istanbul.
"I am afraid of moving there. It could be worse than here," said Mr Halil Yeldkim (38).
Three kilometres away on Hamidije Street, a 51-strong team of British rescue workers was discovering a growing willingness among survivors in Duzce to abandon Muslim burial rites for the sake of the living.
Mr Erdogan Polat, a baker, could see his brother's arm reaching out from the first floor of a collapsed four-storey block. Yet he gave permission for it to be demolished, allowing the rescuers to hunt for survivors rather than spend hours extracting the dead.