TEHRAN – Iran’s influential Shiite clerics have a warning: The country’s sprawling capital is about to be hit by a killer earthquake, and millions will perish.

The reason for the coming apocalypse, the clerics say, is simple: Vice has spread through Tehran, and God intends to punish the sinners.

“Go on the streets and repent for your sins,” Ayatollah Aziz Khoshvaqt, a high-ranking cleric, told worshipers during a recent sermon in northern Tehran. “A holy torment is upon us. Leave town.”

Even among the many urbane inhabitants of this capital of 12 million, the warning of imminent doom has not been taken lightly. Tehran is one of the most earthquake-prone capitals in the world, built on the intersection of two major tectonic plates. More than a hundred fault lines lie beneath the city. A quake in the city of Bam, in eastern Iran, killed tens of thousands in 2003.

Fears about Tehran being hit by “the big one” are not new. But the increased seismic activity worldwide — from earthquakes in remote parts of China to the giant temblor in impoverished Haiti, to say nothing of the recent volcanic eruption in Iceland — has only heightened fears. Never mind that scientists say the timing of a quake is nearly impossible to predict.

“If it is vice that causes earthquakes, there should be floods and volcano eruptions as well in Tehran, because all sins are committed in this huge city,” said an unemployed resident who gave his name only as Maysam.

Khoshvaqt has gone so far as to alert President Mahmoud Ahmadinejad of the danger, according to a website related to Iran’s elite Revolutionary Guard Corps. During a recent speech, Ahmadinejad noted that a cleric had informed him that an earthquake was unavoidable.

Swift action has been taken. Ahmadinejad has announced that the government should start work on programs to help at least 5 million people relocate from Tehran in the coming years. The Tehran-based National Museum of Iran has asked when its 300,000 artifacts can be taken to a safer location.

The earthquake warnings follow weeks of complaints by religious figures about what they deem the loosening of moral standards in the capital, particularly among women who have doffed the traditional Islamic head scarf and long coat with the arrival of spring.

“Women who do not dress modestly … lead young men astray, corrupt their chastity and spread adultery in society, which increases earthquakes,” cleric Hojatoleslam Kazem Sedighi told worshipers in Tehran last week.

Seismology experts are not pleased by the inexpert analysis.

“Belief in God is very good, but we should not put all responsibility on His shoulders,” Bahram Akasheh, a professor of geophysics, said in an interview.

Akasheh is Iran’s most senior expert on earthquakes. He has been studying the ground beneath Tehran for more than 35 years and foresees a bleak future for the capital. There is, he says, a 70 percent chance of a devastating magnitude-7 quake, eventually.

“Half of the population will die. There will be a complete breakdown of all infrastructure. Nearby dams will break. Large fires will erupt. Tehran will become completely uninhabitable,” he said. “There is no way of really avoiding this. We can’t save this city.”