Takeaways from AP investigation into collapse of housing towers during Venezuela's earthquakes

CARABALLEDA, Venezuela (AP) — The collapse of public housing buildings in the Venezuelan state of La Guaira following two catastrophic earthquakes in June can be traced back to their beginnings in 2010, experts and former officials told The Associated Press. The quakes killed more than 6,500 people and left over 17,000 homeless.Here are some takeaways from the AP’s investigation.— In the rush to build homes, the government disregarded dangers posed by the area’s history of mudslides and floods, which could enhance the risks posed by earthquakes. That’s because the buildings would be constructed on the loose, rocky soil that had been deposited there over centuries by floods and mudslides.

The area’s proximity to the San Sebastian Fault line — running off the coast and right underneath La Guaira state — could also compound risks.— Apartment towers went up in the state's parish of Caraballeda as part of the government’s signature housing program. People assigned those apartments were delighted when they finally received the keys, but they did not know that the height of the buildings would make them prone to collapse. That is because buildings that were between 10 and 20 floors could end up swaying at the exact same pace as the seismic waves, in a phenomenon known as resonance.

The syncing results in the building swaying farther and longer, putting additional pressure on columns and increasing the likelihood of damage and collapse, experts said.— With magnitudes of 7.2 and 7.5, the earthquakes were incredibly powerful by themselves. But they also dealt the very type of blow engineers fear most, a near-fault pulse. Central University of Venezuela geologist Michael Schmitz said that when the fault shifted, seismic energy stacked up at the front of the rupture as it moved eastward, delivering “a very strong blow” to the base of buildings, abruptly knocking their support and leaving them unab…