Specialist explains dangers of twin earthquakes; Portugal ‘needs to be prepared’

With the world responding to the devastating twin earthquakes that struck Venezuela yesterday – and total casualties and destruction still far from being accounted for – a leading Portuguese engineering expert has highlighted the unique dangers posed by powerful back-to-back earthquakes.

Infrastructure and geotechnical specialist António Perry da Câmara told SIC Notícias that the two powerful earthquakes that hit within seconds of each other near Caracas yesterday created a significantly higher risk of widespread structural collapse because buildings weakened by the first shock became far more vulnerable to the second.

“If an earthquake measuring 7.2 or 7.5 is already extremely serious on its own, two earthquakes of that magnitude occurring within such a short period inevitably have more severe consequences (…) The first quake causes serious structural damage, meaning the second can bring down buildings that survived the initial shock but were already critically weakened,” he said.

Perry da Câmara stressed that the Venezuelan event was not an aftershock, but two separate earthquakes—a rare phenomenon that has nevertheless occurred twice in recent years (the last time being in Turkey, in February 2023).

Why some buildings survive while others collapse

According to the Portuguese expert, whether a building remains standing depends on several factors, including its age, engineering design and the construction standards in force when it was built.

“Throughout the 20th century, many countries in seismic zones, including Venezuela, progressively adopted stricter earthquake-resistant building codes,” he said. “Today we have a much better understanding of how these events affect structures.”

Modern buildings designed under current engineering standards are intended to withstand earthquakes of this magnitude without collapsing, although they may still sustain significant damage.

“A structure built to today’s standards should theoretically resist an earthquake of this intensity, but not necessarily without suffering damage,” he said.

Perry da Câmara distinguished between conventional earthquake-resistant buildings and those fitted with seismic isolation systems, which are specifically designed to reduce the transfer of ground movement into the structure.

“One thing is a building equipped with seismic isolation, such as part of the new Lisbon Central Hospital. Another is a building simply designed to resist earthquakes. It may not collapse, but there can still be falling objects and internal damage that people need to be prepared for,” he explained.

Portugal better prepared, but improvements still needed

Perry da Câmara believes Portugal is now significantly better prepared for a major earthquake than it was decades ago, thanks to increasingly demanding building regulations.

“Since the 1960s there has been a clear focus in Portugal on seismic resistance,” he said. “More recently, with the adoption of the Eurocodes, new buildings have been designed to withstand much stronger seismic forces than those considered in older regulations.”

However, he noted that only a handful of buildings in Portugal currently use advanced seismic isolation technology.

“As far as I know, there are only two or three buildings in the country equipped with these systems,” he said.

Although seismic isolation cannot eliminate earthquake risk entirely, Perry da Câmara argued that it represents one of the most effective investments available for new construction.

“It is a relatively small addition to the overall construction cost, but it can make the difference between a building collapsing or remaining standing, or at least between suffering major damage and minor damage,” he said.

“Ultimately, that translates into saving lives.”

Portugal lies in one of Europe’s most seismically active regions and remains vulnerable to powerful earthquakes, particularly along the boundary between the Eurasian and African tectonic plates. The 1755 Lisbon earthquake remains one of the deadliest natural disasters in European history, while experts continue to warn that preparedness, resilient infrastructure and public awareness remain essential to reducing the impact of future seismic events.

Source material: SIC Notícias