(CNN) -- Wrenching scenes of survivors being dug out of collapsed schools and apartments after this week's earthquake in central China suggest widespread disregard for building codes in the rapidly urbanizing region, observers said Wednesday.
Rescuers scour the remains of a school in Sichuan province, China, on Wednesday.
"There are lessons to be learned from this, and I think the main lesson is that codes need to be followed," said Reginald DesRoches, a civil engineering professor at the Georgia Institute of Technology in Atlanta.
Although widespread damage from Monday's magnitude-7.9 earthquake was "not terribly surprising," cities like Beijing and Shanghai -- where construction is more closely regulated -- would likely have fared better than the cities of Sichuan province, where the quake's epicenter was, DesRoches said.
"This earthquake may have been larger than the code specified, but it was adequate enough that you'd have satisfactory performance," he said. "What you see in rural areas in particular is that builders just don't have the funds to invest to actually follow the codes, and there are no regulations to do so."
One of the scenes that has drawn the most attention in the wake of the disaster has been in the city of Shifang, where the state-run news agency Xinhua reported more than 2,500 dead and 30,000 people "missing or out of reach" Wednesday. The quake brought down a school full of children and two chemical plants, which leaked more than 80 tons of ammonia, Xinhua reported.
Brian Tucker, a seismologist with the California nonprofit Geohazards International, said China's earthquake danger zones are "very diffused" compared to the United States, where fault zones tend to run in narrow bands.
"The growth in some of these cities is so fast, it would be no mean feat to keep up with it," Tucker said.
Tucker's organization provides technical assistance and advice to help reduce earthquake risks or deaths in developing countries. He said a civil engineer in China has told him the country has no centralized, uniform code for earthquake-resistant public buildings such as schools or hospitals, and the size of the fallen beams and columns pictured in video of the disaster appear inadequate to the task.
"Some of the columns that are broken have exposed rebar that is not tied together essentially with horizontal bands, which makes sure the rebar stays attached to each other and to the concrete," he said.
DesRoches said the collapse of schools was surprising, because they typically are built to tougher standards. But he said many of the buildings that fell were built before 1976, when an earthquake that killed 250,000 people spurred Chinese authorities to require earthquake-resistant construction for many buildings.
And in London, Tom Foulkes, the director-general of Britain's Institute of Civil Engineers, said cities in earthquake zones have to "design accordingly."
Unlike the 1999 earthquake in Turkey, where allegations of widespread corruption in the country's building industry followed an earthquake that killed nearly 20,000 people, Foulkes said that nothing he's seen of the Chinese disaster suggests corruption.
"But it would suggest that the people who've actually built these buildings, maybe paid for them, haven't been able to afford the highest standards, the best materials, the latest designs," he said.
Monday's quake also damaged a major dam near the city of Dujiangyan, but an investigation revealed that the dam is stable and safe, Xinhua reported Wednesday.
Foulkes said China's major dams are well-designed.
"I think the real danger will be from hundreds, maybe thousands, of smaller dams, some of them possibly very ancient, which have never experienced this sort of shock before," he said.
Tucker said school safety was a special concern of his organization. California authorites have closely monitored the construction of schools since a 1933 earthquake in Long Beach killed more than 100 people, many struck by falling debris as they ran out of shaking buildings. Earthquake-resistant buildings there cost about 4 percent more to design and build than other structures, he said.
"It's not rocket science, but it is something that needs some attention," he said.