15 June 2023

Soil liquefaction is still a big issue in Turkey


There is more than just the force of nature behind the widespread building collapses experienced during earthquakes in Turkey. Poor construction practices and bad choices in fact foster soil fragility

by Matteo Cavallito


There is also poor soil management behind the heavy damage count (and casualties) that typically follows earthquakes in Turkey. This is what emerges from a debate that has never died down and is being fueled over time calling into question journalistic investigations and expert warnings. The latest alert came in recent weeks from Sinancan Öziçer, director of the Izmir Chamber of Geophysical Engineers, one of the centers most prone to earthquakes.

Öziçer, in particular, has denounced the dangers associated with construction practices based on an attempt to wrest space from the sea through the expansion of coastal land by land grafting. Against this backdrop, writes Turkish newspaper Daily Sabah, “A possible large-scale earthquake would be devastating for these areas, especially in the western coastal city of Izmir, where districts like Konak and Karşıyaka have the highest population density.”

Soil liquefaction

The concerns are mainly related to a phenomenon known as soil liquefaction. An event, Washington University experts explain, “in which the strength and stiffness of a soil is reduced by earthquake shaking or other rapid loading” Liquefaction, in particular, “occurs in saturated soils, that is, soils in which the space between individual particles is completely filled with water.”

Water exerts pressure on soil particles, affecting their tightness. What typically increases the pressure are seismic tremors, which consequently promote the movement of the particles themselves.

The problem, experts continue, however, is that increased water pressure can also be linked to construction activities. “We need to raise awareness and increase scientific studies that can minimize earthquake damage,” Öziçer added. “The bitter experiences we have had in the past have shown the importance of ground survey projects.”

Coastal lands are the most at risk

The issue has been raising many discussions in Turkey for years. As early as three years ago, for example, the Daily Sabah itself raised the issue of the safety of many buildings in Istanbul, which, with its 15 million inhabitants, is the country’s largest city. “An example of such liquefaction causing collapses was recorded in the 1999 earthquake which killed thousands in northwestern Turkey, including in Istanbul’s Avcılar district,” the newspaper wrote.

The Daily Sabah, on the occasion, quoted in particular the warnings of Istanbul University geophysicist Oğuz Gündoğdu and the director of the local Chamber of Building Engineers, Nusret Suna, who pointed out that land reclaimed from the sea, including coastal boulevards and the Avcılar district in Istanbul, was at high risk of liquefaction.

The other side of Turkey’s construction boom

The development of the construction sector has been one of the main drivers of the economic boom experienced by Turkey during the 21st century. Between 2011 and 2018, British investigative website The Middle East Eye wrote, the construction industry’s annual contribution to the country’s GDP ranged from 7.1 percent to 8.5 percent. After the 1999 earthquake that claimed 17,000 lives in Istanbul, Ankara imposed a new building code designed to ensure greater safety during earthquake events. However, inspections were reportedly poor, and many buildings, including new ones, are now found to be substandard.

In February of this year, a preliminary report by the country’s Chamber of Civil Engineers exposed some critical factors that allegedly contributed to the damage from the earthquake that struck Syria and Turkey a few days earlier.

The report, the World Architecture website wrote, “emphasizes that the regions where earthquake damage is common are the cities planned on fertile agricultural lands.” According to the authors, “in poor ground conditions, even in grounds with the potential to liquefy, 10-15-storey structures with flexible structural systems were severely damaged or demolished altogether.”