The tragedy in Haiti has brought to light the consequences of not having access to clean water. Across the globe, 1.1 billion people do not have access to reliable, clean water and 2.6 billion do not have access to adequate sanitation.

"The last major earthquake that occurred in this area was in 1835. This was a famous earthquake observed by Charles Darwin during his voyage on the Beagle. This is a place where the stress has been gathering for 170 years, and finally it's gone in another earthquake that's repeated this famous historical quake." As is nearly always the case, the region was hit by a series of aftershocks. In the two and a half hours following the 90-second 8.8 event, the US Geological Survey reported 11 aftershocks, of which five measured 6.0 or above.

Saturday's quake was almost 1,000 times more powerful than the one to hit Port-au-Prince in Haiti. But size is not in itself an indicator of the likely number of deaths. One major factor which will limit the number of deaths in Chile will be its greater level of preparedness. Both the Chilean authorities and the Chilean people are generally well versed in how to cope in such an emergency.

The emergency response system is organised at national, regional and local level. "Chile is a seismic country. So, we must be prepared!" is the message from Onemi.

The US Geological Survey (USGS) has recorded numerous aftershocks, the largest of 6.9 magnitude.

As the tsunami radiated across the Pacific, Japan warned that a wave of 3m (10ft) or higher could hit the Pacific coast of its island of Honshu. The BBC's Roland Buerk in Tokyo says the waves so far have been small but officials say worse could still be to come. The biggest wave so far has been just over one metre.

Chile suffered the biggest earthquake of the 20th century when a 9.5 magnitude quake struck the city of Valdivia in 1960, killing 1,655 people.

The quake Saturday, tied for the fifth largest in the world since 1900,

Chile’s government had not yet requested assistance. All international relief groups were on standby, and the International Federation of Red Crosses and Red Crescents said the Chilean Red Cross indicated that it did not need external assistance at this point.

In Talca, 167 miles south of Santiago, almost every home in the center of the city was severely damaged, and on Saturday night, people slept on the streets in the balmy night air near fires built with wood from destroyed homes. All but two of the local hospital’s 13 wings were in ruins, said Claudio Martínez, a doctor at the hospital. “We’re only keeping the people in danger of dying,” he said. Dr. Martínez said the hospital staff had tried to take some people to Santiago for treatment in the morning, but the roads were blocked at the time.

Cellphone and Internet service was sporadic throughout the country, considered one of the most wired in Latin America, complicating rescue efforts.

The earthquake struck at 3:34 a.m. in central Chile, centered roughly 200 miles southwest of Santiago at a depth of 22 miles, the United States Geological Survey reported.

The Geological Survey said that another earthquake on Saturday, a 6.3-magnitude quake in northern Argentina, was unrelated. In Salta, Argentina, an 8-year-old boy was killed and two of his friends were injured when a wall collapsed, The Associated Press reported.

The most powerful earthquake ever recorded was also in Chile: a 9.5-magnitude quake struck in the spring of 1960 that struck near Concepción and set off a series of deadly tsunamis that killed people as far away as Hawaii and Japan.

But that earthquake, which killed nearly 2,000 people and left more than two million homeless at the time, prepared officials and residents in the region for future devastating effects. Shortly after a 7.8-magnitude earthquake struck in Valparaíso in 1985, the country established strict building codes, according to Andre Filiatrault, the director of the Multidisciplinary Center for Earthquake Engineering Research at the University at Buffalo.

In Tehran, Iran’s capital, Dr. Bilham has calculated that one million people could die in a predicted quake similar in intensity to the one in Haiti, which the Haitian government estimates killed 230,000. (Some Iranian geologists have pressed their government for decades to move the capital because of the nest of surrounding geologic faults.)

Ali Agaoglu, a Turkish developer ranked 468th last year on the Forbes list of billionaires, described how in the 1970s, salty sea sand and scrap iron were routinely used in buildings made of reinforced concrete. “At that time, this was the best material,” he said, according to a translation of the interview. “Not just us, but all companies were doing the same thing. If an earthquake occurs in Istanbul, not even the army will be able to get in.”

Istanbul stands out among threatened cities in developing countries because it is trying to get ahead of the risk. A first step was an earthquake master plan drawn up for the city and the federal government by Dr. Erdik’s team and researchers at three other Turkish universities in 2006. Such a plan is a rarity outside of rich cities like Tokyo and Los Angeles.Carrying out its long list of recommendations has proved more challenging, given that the biggest source of political pressure in Istanbul, as with most crowded cities, is not an impending earthquake but traffic, crime, jobs and other real-time troubles.Nonetheless, with the urgency amplified by the lessons from Haiti’s devastation, Istanbul is doing what it can to gird for its own disaster.

But a push is also coming from the bottom, as nonprofit groups, recognizing the limits of centralized planning, train dozens of teams of volunteers in poor districts and outfit them with radios, crowbars and first-aid kits so they can dig into the wreckage when their neighborhoods are shaken.

Under a program financed with more than $800 million in loans from the World Bank and the European Investment Bank, and more in the pipeline from other international sources, Turkey is in the early stages of bolstering hundreds of the most vulnerable schools in Istanbul, along with important public buildings and more than 50 hospitals. With about half of the nearly 700 schools assessed as high priorities retrofitted or replaced so far, progress is too slow to suit many Turkish engineers and geologists tracking the threat. But in districts where the work has been done or is under way — those closest to the Marmara Sea and the fault — students, parents and teachers express a sense of relief tempered by the knowledge that renovations only cut the odds of calamity.

“I hope it’s enough,” said Serkan Erdogan, an English teacher at the Bakirkoy Cumhuriyet primary school close to the Marmara coast, where $315,000 was spent to add reinforced walls, jackets of fresh concrete and steel rebar around old columns and to make adjustments as simple as changing classroom doors to open outward, easing evacuations. “The improvements are great, but the building may still collapse,” he said. “We have to learn how to live with that risk. The children need to know what they should do.”In a fifth-grade classroom, the student training that goes with the structural repairs was evident as Nazan Sati, a social worker, asked the 11-year-olds what they would do if an earthquake struck right at that moment. At first a forest of hands shot toward the ceiling. Ms. Sati quickly told them to show, not tell. In a mad, giggling scramble, the students dove beneath their desks. But the threat for children, and their parents, also lies outside the school walls, in mile upon mile of neighborhoods filled with structures called gecekondu, meaning “landed overnight,” because they were constructed seemingly instantly as hundreds of thousands of migrants from rural regions flowed into the city seeking work in the past decade or two.