On 16 September 1978, at five past seven in the evening, a magnitude 7.4 earthquake struck central Iran. The town of Tabas was very largely destroyed. At least 15,000 people were killed, and some estimates put the number considerably higher. The shaking reached a maximum Mercalli intensity of IX, violent.
Most houses there were built of thick mud brick, with heavy roofs. Walls of that kind are strong when weight presses straight down on them, and weak when the ground pushes them sideways. They crack, then they fall, and they fall inward, onto the rooms below. It was evening, and people were at home.
Tabas sits in desert, a long way from any large city. Help had to travel that distance before it could begin, and the first hours after a collapse are the hours that matter most. Afterwards, engineers and seismologists went to the site, measured what had failed and how, and published what they found. Those surveys became part of the technical record on unreinforced earthen construction, and are still cited.
The Wikipedia article is linked below, for anyone who wants the fuller account.
Tabas was known for its date palm gardens, watered by channels out of the desert. Some of the palms stood through the shaking, and more were planted as the town was rebuilt around them. Slow trees, patient work.
Tabas sits on the southern edge of the Dasht-e Kavir, with hundreds of kilometres of desert road between it and the nearest large city. Rescue convoys had to cross that ground before anyone could begin digging, and the hours it took were the hours that counted.