Source: Wikimedia Commons
An interesting map was
published by the US Geological Survey shortly after the Turkish-Syrian earthquakes.[1] It showed (perhaps
somewhat predictively) that there was only one tiny square of the vast affected
area in which Modified Mercalli intensity (which is largely a measure of
damage) reached 9.0, the 'violent' level.[2] This is--just
about--enough to damage very significantly a well-engineered structure (but not
necessarily enough to bring it crashing down). Although the disaster of 6th
February 2023 produced, in fact, stronger shaking than this (maximum 1.61g), it should not have
caused 5,500 large buildings to collapse as large parts of the epicentral area had accelerations <0.6g, a design level for antiseismic construction in areas of known high seismicity. The disaster in Turkey and Syria is
very obviously the result of poor construction. This is painfully visible in
the video images of buildings collapsing. The patterns of collapse are also the
same as those in the last dozen Turkish earthquakes, although they are doubtless
more extensive this time around.
In 43 years of studying disasters I have seen few events that so clearly illustrate the primacy of vulnerability over hazard impact as does the Turkish-Syrian earthquake sequence of February 2023. Work at universities in Florida and Colorado strongly suggests that corruption is the principal cause of earthquake disaster, world-wide. The Turkish anti-seismic building codes have been revised five times in the last 55 years, including a thorough and intelligent upgrade in 2018. However, in 2016 and at nearly 20 other times there were amnesties that decriminalised those in the construction industry who ignored the laws, and those who modified buildings in ways that stopped them from being compliant with the regulations. Such practices were extremely widespread, the norm rather than the exception. This is also my experience from having spent extended periods in such buildings in Anatolia.
Building codes in Turkey are now perfectly good enough. The
tragedy lies in their non-observance and the paucity of retrofitting. It is a
mixture of simple errors, lax procedures, ignorance, deliberate evasion,
indifference to public safety, untenable architectural fashions, corruption and
failure to enforce the codes. Many, perhaps most, people in Turkey live in
multi-storey, multiple occupancy reinforced concrete frame buildings. It is
these that collapse. Most of them are highly vulnerable to seismic forces.
There is plenty of engineering literature on the typical seismic performance
defects of such buildings in Turkey. Perhaps we can grant a small exception for
Syria, although before the civil war it did have building codes and earthquake
research. However, the comment by a leader of the Syrian Catholic Church that
buildings had been weakened by bombardment was something of a red herring. This
probably affected about 2-3% of those that collapsed.
To know whether a reinforced concrete
building is safe to live in would require knowledge of:-
- the shear resistance (i.e., quality) of the concrete
- the presence or absence and connectivity of shear walls
- whether there are overhangs or other irregularities of plan that distribute the weight of the building unevenly or concentrate load on particular parts of it
- the presence or absence of a ‘soft-storey’ open ground floor which concentrates the load above columns that cannot support it during seismic deformation
- the connections between beams and columns, especially how the steel reinforcing bars are bent in
- whether there are proper hooks at the end of rebars on concrete joints
- whether the rebars were ribbed or smooth
- the quality of the foundations and the liquefaction, landslide or subsidence potential of the underlying ground
- the state of maintenance of the structural elements of the building
- any subsequent modifications to the original construction (e.g. superelevations).
An experienced civil engineer could evaluate some of that by eye, but much of the rest is hidden and only exposed once the building collapses. A short bibliography of sources that deal with common faults in Turkish R/C construction is appended at the end of this article.
Many of the news media that have
reported the disaster have presented it as the result of inescapable
terrestrial forces. While that cannot be negated, it is less than half of the
story. The tragedy was largely the result of highly preventable construction
errors. Vox clamantis in deserto: to examine this aspect of the disaster
one would have to face up to difficult issues, such as corruption, political
decision making, people's expectations of public safety, and fatalism versus
activism. How much simpler to attribute it all to anonymous forces
within the ground!
A well-engineered tall building that collapses will leave up to 15% void spaces in which there may be living trapped victims. It was notable that, in many buildings that pancaked in Turkey and Syria, the collapses left almost no voids at all, thanks to the complete fragmentation of the entire structure--i.e., total loss of structural integrity. This poses some serious challenges to search and rescue. In some cases the collapse was compounded by foundation failure, leading to sliding or rotation of the debris.
There was also an interesting dichotomy in the images on television between the "anthill" type of urban search and rescue, carried out by people with no training, no equipment and no idea what to do, and professional urban search and rescue (USAR), which sadly was in the minority of cases. Nevertheless, it remains true that the influx of foreign USAR teams is, sadly, both riotously expensive and highly inefficient, as they tend to arrive after the 'golden period' of about 12 hours in which people could be rescued in significant numbers.
Among the damage there is at least one classic example of the fall of a mosque and its minaret, the same as that which happened in the Düzce earthquake of 1999. Mosques are inherently susceptible to collapse in earthquakes: shallow arches, barrel vaults, rigid domes and slender minarets. The irony is that the great Turkish architect of the 16th century, Mimar Sinan (after whom a university in Istanbul is named) had the problem solved. He threaded iron bars through the well-cut stones of his minarets, endowing them with strength and flexibility. It is also singular that one of the first short, stubby minarets in Turkey (located in Izmir) was built 300 years after Sinan died in 1588.
The earthquakes chart a map of illegal and ineffective construction methods. Relatively few Turkish mass media openly discuss this (exceptions are KSL-NewsRadio and Bianet), and those that do are at risk of being treated as criminals. Nevertheless, the only way for reconstruction to succeed is for there to be a radical change in Turkish policy towards building practices. The issuance of a hundred prosecution notices to builders and engineers is a somewhat hypocritical response, given the amnesty they enjoyed. It shows that political responses to disasters depend on the electorate's short memory.
The President of Turkey has publicly vowed to "reconstruct thousands of houses within one year". This is not a good idea. It should take two or more years to conduct geotechnical survey (microzonation) and urban planning. More time is required for necessary public consultation on the plans. Failure to recognise that time is socially necessary in reconstruction risks marginalising the problems involved rather than facing up to them.
Finally, there is a seismic hazard map of the area affected by these earthquakes. It was made in 1967 and events have shown it to be substantively accurate. No one can say that the risk was not well known, or that the events were unexpected.
Select Bibliography of Sources on Turkish R/C Construction Practices
Cogurcu, M.T. 2015.Construction and design defects in the residential buildings and observed earthquake damage types in Turkey. Natural Hazards and Earth System Sciences 15: 931-945.
Dogan, G., A.S. Ecemis, S.Z. Korkmaz, M.H. Arslan and H.H. Korkmaz 2021. Buildings damages after Elazığ, Turkey earthquake on January 24, 2020. Natural Hazards 109: 161-200.
Dönmez, C. 2015. Seismic performance of wide-beam infill-joist block RC frames in Turkey. Journal of Performance of Constructed Facilities 29(1): 1-9.
Erdil, B. 2017. Why RC buildings failed in the 2011 Van, Turkey, earthquakes: construction versus design practices. Journal of Performance of Constructed Facilities 31(3):
Korkmaz, K.A. 2009. Earthquake disaster risk assessment and evaluation for Turkey. Environmental Geology 57: 307-320.
Ozmen, H.B. 2021. A view on how to mitigate earthquake damages in Turkey from a civil engineering perspective. Research on Engineering Structures and Materials 7(1): 1-11.
Sezen, H., A.S. Whittaker, K.J. Elwood and K.M. Mosalam 2003. Performance of reinforced concrete buildings during the August 17, 1999 Kocaeli, Turkey earthquake, and seismic design and construction practise in Turkey. Engineering Structures 25(1): 103-114.
Corruption and Earthquake Disasters
Ambraseys, N. and R. Bilham 2011. Corruption kills. Nature 469: 153-155.
Escaleras, M., N. Anbarci and C.A. Register 2007. Public sector corruption and major earthquakes: a potentially deadly interaction. Public Choice 132: 209-230.
