Bam was asleep. It was 5:26 a.m. on Friday, December 26, 2003 — a winter morning in the desert city of Bam in Kerman province, southeastern Iran — when a magnitude 6.6 earthquake struck almost directly beneath it. The U.S. Geological Survey places the rupture on the Bam Fault, at a depth of about 10 kilometres, with the strongest shaking, intensity IX, recorded at Bam itself.
Estimates vary, as they often do after a disaster of this scale, but the USGS summary puts the toll at around 31,000 people killed, 30,000 injured and 75,600 left homeless, with about 85 percent of buildings in the Bam area damaged or destroyed. A moderate earthquake had levelled a city — not because it was exceptionally large, but because of what it struck: a city built largely of mud brick, at the hour when almost everyone was home in bed.
The Bam earthquake was a strike-slip event, driven by the slow collision of the Arabian Plate moving northward against the Eurasian Plate — at roughly 3 centimetres a year, according to geological studies of the region. The rupture ran along the Bam Fault between Bam and neighbouring Baravat, and instruments in Bam recorded peak ground acceleration of about 0.98g — nearly the full force of gravity, sideways.
That number explains a lot. Ground that accelerates that hard does not gently shake a building; it throws it. For a framed, reinforced building, survival is at least possible. For an unreinforced mud-brick house, it was not.
Most of Bam's homes were one or two storeys, built from mud brick or other unreinforced masonry — materials that are heavy, brittle, and held together with little that can bend. When they failed, they did not leave the pockets and voids that survivors are sometimes found in inside framed buildings. They came down as heavy mud and debris, in the dark, in winter cold, over people who never woke up.
The damage reached the city's lifelines too. Bam's hospitals were severely damaged, complicating care for the tens of thousands injured, who had to be treated in the open or moved to other cities. Rescue, as in so many pre-dawn disasters, began with neighbours digging with their hands.
Above the city stood Arg-e Bam, widely described as the largest mud-brick structure in the world — a fortified citadel around 2,000 years old, on the old Silk Road. The earthquake badly damaged it, toppling walls and towers that had stood for centuries. Its loss was not the human loss, and no account of Bam should confuse the two. But it showed, in a single image the world could understand, how completely the shaking had undone even the city's most enduring landmark. Bam and its cultural landscape were added to UNESCO's World Heritage List in 2004, and painstaking reconstruction of the citadel has continued since.
Bam became one of the clearest case studies in earthquake risk: magnitude is only the beginning of the story. A 6.6 far from people, or under a city built to modern codes, is a serious event. The same 6.6 at shallow depth, at 5:26 in the morning, under unreinforced mud-brick housing, is a mass-casualty disaster. As with İzmit in 1999 and Christchurch in 2011, the verdict afterwards fell less on the geology than on the buildings.
The work that follows a quake like Bam is unglamorous: enforce the codes that already exist, retrofit or replace the housing stock that cannot survive shaking, and stop treating traditional materials as safe simply because they have stood for a long time. Arg-e Bam had stood for a very long time too — until the one morning the fault underneath it moved.
Read what to do before an earthquake, during, and after.