Editor's note: New estimates for what a 7.0 earthquake could do to the Wasatch Front are scary: It could kill more than 6,000 people, injure 90,000 and cause a $40 billion economic hit. In a five-part series, the Deseret Morning News describes such a future quake — as if worst-case scenarios proved to be true.

Over the decades, Wasatch Front residents built, sold and resold tens of thousands of pretty brick homes. Unfortunately, such houses — at least those that lacked seismic upgrades — turned out to be death traps in Utah's great 7.0 earthquake of 2008.

It was not just homes. It was all masonry buildings without reinforcing steel. Too many of the brittle structures could not flex well with strong ground shaking on the wintry afternoon of Feb. 1, so many buildings snapped like chalk and fully or partially collapsed. That included many schools, where casualty numbers were staggering; churches; government buildings and businesses — but mostly houses.

Some such buildings — as well as many of other construction types — dodged damage because of recent seismic upgrades to them, including such landmarks as the state Capitol, Salt Lake City-County Building and the Tabernacle.

Also, for example, a few school districts that had spent hundreds of millions of dollars on seismic upgrades fared well, but those that did not saw scores of schools severely damaged. Sadly, as had been predicted back in 2006, more than 700 students and teachers were killed in schools, and another 13,000 were injured.

Many hospitals paid for being too near faults and landslide areas.

Recent rebuilding of many bridges allowed them to survive, but a high number of older ones — built mainly in the 1960s and '70s as interstate freeways were constructed — were damaged or failed.

But the worst news of all for structures still came from those "unreinforced masonry" buildings.

Unreinforced masonry

Warnings had been given about unreinforced masonry buildings for years. Steve Bartlett, a University of Utah assistant professor of civil and environmental design, said during a 2006 community meeting on quakes that they are "the single largest threat to loss of human life" in an earthquake.

He was right, and their failures contributed greatly to the 6,200 deaths and 90,000 injuries in the 2008 quake — numbers close to those predicted in 2006 by Bob Carey, earthquake specialist for the state Office of Emergency Services, using computer modeling.

Barry Welliver, a structural engineer and chairman of the Utah Seismic Safety Commission, had also warned in 2006 that such structures "are the single worst performers in an earthquake" — and many could suffer severe damage in earthquakes as small as 5.0 on the Richter scale, let alone the 7.0 that hit in 2008.