The two earthquakes that hit Venezuela on Wednesday had a magnitude of 7.2 and 7.5 on the Richter scale. It came within 39 seconds. The latest information speaks of 920 dead and 3600 injured. More than 46 thousand people are missing.
It will take some time to assess the full extent of the damage. One of the worst affected places is the town of La Guaira. It is considered the gateway to Venezuela, as one of the country’s most important ports is located there. There are entire blocks of collapsed buildings in the photos and videos. The basic infrastructure is in ruins, writes the Los Angeles Times.
When we look at the footage, at first glance we can see that concrete structures without steel reinforcement have collapsed, said Marie Mohammed, president of the Southern California Association of Structural Engineers.
According to her, concrete is strong in compression, but fragile and weak in tension. Strong tensile and shear forces act on the building during lateral shocks. Concrete without steel does not have the necessary ductility, so the material cannot withstand tension and the walls will suddenly fall apart, describes Mohammedová. During seismic shocks, such buildings easily crack and collapse.
Although building regulations have changed since the 1970s and prohibited the construction of these buildings, until then a large number of them had been built and most of them were not reconstructed. In the last decade, the city halls of some cities, such as Los Angeles, Torrance, Santa Monica and West Hollywood, have requested seismic modifications of vulnerable buildings, but they are few compared to the total number.
In addition, the seismic risk of Caracas is similar to the risk of Los Angeles and San Francisco, because all three cities are located near the border of tectonic plates, seismologist Lucy Jones said.
The speed with which the tectonic plates are moving relative to each other in Venezuela is similar to how quickly seismic stress builds up on the San Andreas fault in California, Jones added. “What happened in Venezuela is the type of earthquake we’re talking about in the case of San Andreas in California,” added Jones.
It is not only the United States where there are a large number of such buildings. During an earthquake, they collapsed, for example, in Taiwan in 1999, in New Zealand in 2011, in Mexico in 2017, in Turkey and Syria in 2023, and in June also in the Philippines.
