5 minute read
Withstanding disaster
How can we ensure that buildings survive earthquakes?, asks Professor Sinan Acikgoz, Fellow in Civil Engineering. He finds previous assumptions shaken to their foundations.
Two earthquakes occurred in south-eastern Turkey and north-western Syria on 6 February 2023. The media reported tens of thousands of fatalities caused by the 7.8 and 7.5 magnitude quakes. However, it wasn’t the numbers that alerted me to the gravity of the situation. It was the stories of the survivors and emergency workers. Sounds coming from the rubble. Rescuers crawling in extremely confined areas to reach survivors. People burying their own dead.
One month after the earthquakes, an opportunity arose for me to go to the disaster zone in Turkey with the Earthquake Engineering Field Investigation Team (EEFIT). EEFIT had organised similar missions in the past and shared findings with the engineering and seismology community. I was optimistic these efforts could also help people in the region as many buildings had not yet been assessed by engineers.
Nevertheless, my initial optimism gave way to doubt. Don’t we already know everything about how to make buildings safe against earthquakes? After all, it takes only one look for experienced earthquake engineers to identify design deficiencies. Many of my colleagues argued that the damage was due to poor governance and extensive corruption. Besides, some Turkish state establishments had treated researchers from foreign institutions with caution; would we be able to access the region and help in a meaningful way?
I went to the disaster zone uneasily, fearing that the only clear beneficiary of the mission would be us, its attendants. These doubts quickly vanished as we entered cities ravaged by the earthquakes. The scale of destruction was (and still is) hard to describe. It dawned on me that these places would need help from anyone and everyone just to exist again.
My research deals with understanding the mechanical behaviour of historic masonry structures. In this specific field, we know far less than we should. The construction techniques and materials used internally in structural components and foundations are often hard to characterise. As a result, even with sophisticated modelling tools, we cannot predict with certainty whether a building would be able to withstand an earthquake. This, above all, is our task as engineers. If we cannot answer this question, we cannot claim to know enough, let alone know everything.
As we travelled across the earthquake zone, we listened to people’s stories and tried to imagine what had happened. We also formulated theories, to explain why structures failed and why the damage was so extensive. Some of us suggested that the historic construction techniques were problematic: if only the walls had been built using diatons (large stones that extend along the thickness of the walls) or timber tie beams and metal reinforcements linking the stones, then surely the buildings would have survived. Others were worried about modern interventions to historic buildings which did not function as intended. However, could we be sure the buildings would have fared better without these interventions?
On state TV, a media campaign had begun, describing the earthquakes as the ‘disaster of the century’ and highlighting how the ground shaking was stronger than expected. But modern earthquake engineering codes require buildings to ensure life safety regardless of the earthquake size. So, where did it all go wrong?
Centuries-old monuments and engineered multistorey buildings collapsed in the centre of the ancient city of Antakya (Antioch), while shoddy constructions in the hills survived (see photo). Earthquake records suggest that this may have been due to the amplification of ground motions in the alluvial deposits underlying the city centre, leading local governments to question its future location. Should the city be rebuilt in the same place? Doubtless, similar questions were asked by the past residents of Antioch, which was rebuilt many times over the two millennia of its history. Don’t we have the technology to rebuild safely this time, knowing it is likely that the residents of Antakya will return? Will we be able to do it in a way that preserves the unique culture of the city?
Stories help us empathise, but there can be a dangerous side to them. Focusing on a single cause for the destruction could give the impression that a quick fix is possible. The reality is that failings at every level transformed this natural hazard into a disaster. The only way to address catastrophic earthquakes is for all stakeholders to investigate and acknowledge their own failures. Until we do so, we will only be fooling ourselves by asserting ‘we know everything about protecting people and buildings from earthquakes’. For engineering researchers, this means developing practical tools to answer the only question that matters: ‘how can we ensure that this building survives a likely future earthquake?’.
