Earthquake in Venezuela: Unstable soils and construction defects worsened the disaster

The two magnitude 7,2 and 7,5 earthquakes that struck Venezuela on June 24th left more than 6.000 dead and thousands missing. In La Guaira, the nature of the soil, deficiencies in the reinforcement, and possible construction defects explain the scale of the collapses, according to several experts.

In Catia La Mar, in the state of La Guaira, 42-year-old Jennire García and her family are now living in tents set up in front of their building. The building is still standing, but large cracks threaten its stability.

The two successive earthquakes of magnitude 7,2 and 7,5 that struck northern Venezuela caused the collapse of 190 buildings and damaged 856 others. La Guaira, located about thirty kilometers northwest of Caracas, is the area most affected by the casualties and damage.

Loose soils amplify the tremors.

According to Feliciano De Santis, president of the Venezuelan Society of Geologists, part of La Guaira rests on "unconsolidated" soils. Any construction in this area would therefore require in-depth geotechnical studies.

The state had already been affected in 1999 by a landslide that caused several thousand casualties.

"From a geological perspective," the 27 years separating the two disasters represent "a millisecond." "These soils generally tend to be loose soils," explains Feliciano De Santis.

According to the geologist, the characteristics of the terrain caused an "amplification of the seismic signal": the ground moved with an intensity greater than that which would have been observed on a more stable subsoil.

The residential complex where Jennire García lived, built after the 1999 disaster, has been declared uninhabitable. Deep cracks run through its walls, several balconies have detached, and some towers have collapsed.

More than 23.000 people are currently housed in shelters, according to official figures. Nearly 22.000 homes have suffered serious damage or are considered to be at high risk, representing 40% of the buildings assessed.

Defects observed in the reinforcements

Venezuelan authorities have updated earthquake-resistant regulations since the 1967 earthquake, with the latest update in 2019. In La Guaira, however, some newer buildings have construction defects, according to Japanese engineer Kit Miyamoto, who is inspecting the area with support from Washington.

"There seems to be a lot of steel, it looks very good. But the reinforcements are supposed to go deep into the foundations for solid support. That's not the case." observes Kit Miyamoto.

Rescuers are continuing their search in the rubble of residential complexes that could reach 12 stories and have up to 16 apartments per level.

Sixteen collapsed social housing towers

Between 2011 and 2013, 43 towers known as OPPEE were built as part of social housing projects under the presidency of Hugo Chávez. Sixteen of them collapsed on June 24, killing hundreds. Others remained standing but sustained serious structural damage, according to the investigative news site Armando.info.

The extent of the damage is explained by "contracts awarded arbitrarily to companies with no prior experience." according to an investigation byarmando.info.

In Caracas, Chacao is the most affected municipality, with 68 deaths, three collapsed buildings and several dozen uninhabitable buildings.

The majority of the buildings that collapsed in the metropolitan area had been built before the magnitude 6,6 earthquake in 1967, according to the Venezuelan Order of Engineers.

The buildings "had survived, some had been reinforced," emphasizes Félix Ojeda, representative of the Order of Engineers of Venezuela.

Demolish buildings beyond repair

For Kit Miyamoto, the next steps will need to distinguish between buildings that can be repaired and those whose demolition has become inevitable.

The "obvious next step" is to "demolish the buildings" beyond repair and "repair everything that can be repaired." the Japanese engineer believes.

"It's simply a matter of preparing a clean slate so that people can invest there again," adds Kit Miyamoto.

4.000 homes announced starting this year

Criticized for the slowness of her response during the disaster, interim president Delcy Rodríguez has pledged to deliver approximately 4.000 homes starting this year.

The leader also announced a law aimed at encouraging the rental of housing and launched a census to identify future beneficiaries of social housing.

Jennire García has registered, but is still waiting for a relocation solution.