People and rescuers work on the debris of a collapsed building in Caracas after a pair of strong earthquakes struck Venezuela.
Edilzon Gamez/Getty Images
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Edilzon Gamez/Getty Images
A single significant earthquake hitting Caracas, where many older structures are susceptible to intense shaking, could result in extensive destruction. However, two occurring within a minute created a particularly devastating situation, according to William Barnhart, a geophysicist at the U.S. Geological Survey in Golden, Colorado.
Barnhart explains that a 7.2 magnitude earthquake would be catastrophic on its own. “But 39 seconds later, it was followed by a 7.5 magnitude earthquake, which is approximately three times more powerful,” he adds.
The proximity of these earthquakes to densely populated regions on land amplified their lethality. “It’s a terrible tragedy,” Barnhart laments.
The exact cause beneath the Earth’s surface remains uncertain, but Barnhart suggests the earthquakes may have originated from two distinct faults. This region is characterized by a complex network of intersecting faults.
“There’s not just a single easily identifiable fault that you can point to and say, ‘The earthquake definitely happened on this fault,'” Barnhart points out.
Traditionally, earthquake risk assessments have not always considered the possibility of multiple faults being involved, notes Chris Goldfinger, a paleoseismologist at Oregon State University. “We generally assume earthquakes will occur on one fault only,” he explains.
Goldfinger recalls that the 2016 KaikÅura earthquake in New Zealand, which involved multiple faults, surprised many and reshaped scientific understanding of fault interactions. If Venezuelan earthquakes are similar, this could be crucial for studying such risks.
“The first instance was entirely unexpected. We had no indication that it could occur,” Goldfinger remarks. “Now, a decade later, two significant earthquakes have struck on separate faults.”
Globally, other regions with intricate fault systems exist, such as California’s San Andreas Fault.
A recent study suggests that parts of the San Andreas and San Jacinto fault systems might currently be under their greatest stress levels in at least 1,000 years. Experts believe California is significantly more prepared for such events compared to Venezuela.
Such a level of preparedness is uncommon, Goldfinger observes, as engineering often lags behind the rapid advancements in earthquake science.
“Many structures globally were constructed before the understanding of plate tectonics,” he states. “Retrofitting entire cities is an overwhelming challenge.”
In quick succession, the Venezuelan earthquakes were followed by others in Japan and California. Barnhart clarifies, “As far as we know, these earthquakes are entirely unrelated.”
He adds that although the Venezuelan earthquakes were unusual, their timing alongside two unrelated quakes on the same day is not as surprising as it might seem.
“Earthquakes are frequent,” Barnhart explains. “Most go unnoticed because they occur at sea and affect no one.”
