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Assessing Damage and Advancing Resilience: Insights from the 2023 Turkey-Syria Earthquake Reconnaissance Mission

By:

Luis Martins

Anirudh Rao

Sep 27, 2023

The February 2023 Turkey–Syria Earthquake: A Reconnaissance Mission Supported by USAID’s BHA

The February 2023 Turkey–Syria earthquake caused widespread devastation in both countries, with 50,783 confirmed fatalities in Turkey and 8,476 in Syria. As part of a damage reconnaissance mission supported by USAID’s Bureau for Humanitarian Assistance (BHA), a team comprising members from the United States Geological Survey (USGS), Kandilli Observatory and Earthquake Research Institute (KOERI) in Istanbul, Middle East Technical University (METU) and Hacettepe University in Ankara, and the Global Earthquake Model Foundation (GEM) visited some of the cities and towns most heavily affected by the earthquakes, including Narlı, Pazarcık, Kahramanmaraş, Gaziantep, Türkoğlu, Nurdağı, Fevzipaşa, İslahiye, Hassa, Kırıkhan, Antakya, İskenderun, and Osmaniye.


The mission team included:

  • KOERI (İstanbul): Prof. Ufuk Hancilar (earthquake risk), Prof. Eser Çaktı (earthquake engineering), Tuğçe Tetik (PhD student), Onur Altay (PhD student)

  • METU (Ankara): Prof. Ayşegül Askan (engineering seismology), Prof. Murat Altuğ Erberik (earthquake engineering), Gamze Muratoglu (PhD student), Mehmet Fırat Aydın (MS student), Kubilay Albayrak (PhD student)

  • Hacettepe Üniversitesi (Ankara): Prof. Mustafa Koçkar (engineering geology)

  • USGS (Golden): Kishor Jaiswal (PAGER)

  • GEM (Pavia): Luís Martins (vulnerability modelling), Anirudh Rao (risk modelling)

 

Extensive Seismic Recording: The Turkish National Strong Motion Network

The Turkish National Strong Motion Network operated by the Disaster and Emergency Management Authority of Turkey (AFAD) has 379 seismic stations that recorded the strong ground motions from the first, Mw 7.8 earthquake, and 387 seismic stations for the second, Mw 7.7 earthquake. The field survey team focused on conducting rapid damage surveys and assigning overall damage grades to buildings in the immediate vicinity of the recording stations in the visited towns and cities.

 


Mission Objectives: Assessing Seismic Vulnerability

Since our visit was to occur four months after the devastating earthquakes, we were aware that the landscape of the affected region had changed dramatically. Collapsed and severely damaged buildings had largely been removed, leaving empty lots scattered throughout the affected towns and cities. Our initial plan was to focus on buildings in the immediate vicinity of recording stations, observe the performance of modern code-conforming RC buildings, collect building attributes and assign damage grades systematically, and cover as much area as possible given constraints. We were also mindful of not duplicating the assessments already carried out by previous teams in the immediate aftermath. One of the primary objectives of our trip was to improve our understanding of the seismic vulnerability of modern code-conforming RC buildings in the affected areas that were subjected to very high levels of ground shaking.

 

Field Survey: Rapid Damage Surveys and Data Collection

The reconnaissance team surveyed more than 500 buildings in the areas affected by the earthquake over a period of five days, collecting information about the prevalent building typologies, construction age, and structural and non-structural damage patterns. The surveyed towns and cities were mostly located along a route closely following the Mw 7.8 earthquake’s rupture plane and located in the immediate vicinity of recording stations.


Seismic stations that recorded the Mw 7.8 Kahramanmaraş earthquake


Seismic stations that recorded the Mw 7.7 Elbistan earthquake


Towns and cities visited by the field survey team


In order to collect the data a custom application was designed for this mission using the Fulcrum® mobile data collection app ecosystem. The application was divided into three main portions: (i) identification of the surveyor, (ii) identification of the building and (iii) evaluation of the damage grade. The first portion consisted of a simple recording of the member of the mission who was in charge of that specific data point. The second collected data on the location of the building, number of storeys above and below ground, type of lateral load resisting system, occupancy type and irregularities. The last portion of the application was dedicated to the estimation and documentation of the level of damage and estimated loss level.

 


 

Survey Findings: From Narlı to Osmaniye


 

Day 1: Narlı - A Town of Slight to Moderate Damage

We started the first day of the mission at Narlı, a small town consisting mainly of low-rise buildings that experienced slight to moderate damage.



Day 1 Continued: Pazarcık - High Shaking and Infrastructural Challenges

The next stop was the city of Pazarcık, where station 4614 recorded a peak ground acceleration (PGA) of over 2.0 g in both horizontal directions and a short period spectral acceleration SA (0.2s, 5% damping) in the N-S direction of over 7.5 g. The building stock in this town comprised mostly mid-rise reinforced concrete moment-resisting frames (RC MRFs) with unreinforced masonry infill walls. Almost all of the buildings we saw had some damage, at least on the infill walls. Collapsed buildings have already been removed, and heavily damaged buildings are in the process of being demolished. AFAD has set up temporary shelters using containers in the town. In general, people living in moderately damaged buildings have been asked to evacuate, and the building owners have been given one year to repair (including retrofit) the buildings. Most mid-rise buildings had suffered some significant damage.






Day 2: Türkoğlu - Surprising Resilience Amid Industrial Damage

The second day of the trip started in the town of Türkoğlu, where some severe damage to industrial buildings was observed. The short-period spectral acceleration SA(0.2s) recorded at station 4616 in this town, in the N-S direction was almost 2.5 g, with a geometric mean of the two horizontal components of around 1.5 g. However, we observed only slight damage to the 1-2 storey RC MRF single-family residential buildings around the station despite the extreme level of shaking. The other typical structural type in Türkoğlu is a 6-7 storey RC MRF with infill walls and multi-family residential apartment buildings. A substantial fraction of these have at least moderate damage, with all infill walls heavily damaged, and these buildings have been evacuated. In many of these buildings, the structural members have little damage - it's the heavy damage to the interior and exterior walls that has led the buildings to be uninhabitable. There are also 1-2 storey concrete block masonry single-family houses around this station with very little damage. We also saw a stone masonry mosque near the station that was built just last year and had not a single crack. Many families are still living in tents set up outside their own damaged buildings.




Day 2 Continued: Nurdağı - Older Buildings and Ongoing Demolition

This was followed by a stop in the town of Nurdağı. The building stock in Nurdağı is older than that in Türkoğlu. The prominent building type around the seismic station and in the centre of the town is 6-7 storey RC MRF multi-family residential apartment buildings. More than half of these mid-rise buildings collapsed or were heavily damaged, and most of the remaining have moderate structural damage but with all of the partition walls destroyed. Demolition and debris removal works were ongoing all around the town at the time of our visit, and the air was heavy with dust and cement and asbestos particles, so we limited the time spent outside in Nurdağı.




Day 3: Kahramanmaraş - Collapse and Evaluation

The third day started in Kahramanmaraş. The first residential building complex we visited was Güneşli Kocabaş, which had 16 buildings each of 14-15 storeys, which appeared to have been constructed using the tunnel-form system. One of the buildings in this complex collapsed, and the remaining were deemed unsafe and thus were commissioned to be demolished. In the immediate surroundings of this complex, there were several 1-2 storey reinforced concrete frame buildings and some unreinforced masonry houses with only slight damage or even no damage.




We also visited a second residential apartment complex in Kahramanmaraş at Doğukent, which had a mix of RC MRFs and RC dual systems – no collapses or fatalities were reported at this location, but most of the buildings had heavy damage to the partition walls.



Day 3 Continued: Fevzipaşa - Significant Damage Amidst Striking Performance

The day continued with a stop at Fevzipaşa where peak ground accelerations in excess of 1.0 g were recorded in all three directions at station 2708. The effects of the high vertical acceleration were especially evident from the displaced roof tiles. We were on top of a small hill very close to the station, where we surveyed a residential apartment complex comprising a dozen identical six-storey RC MRFs (possibly constructed through TOKİ) with nearly similar moderate damage. These buildings typically all had damage to the beams in the basement and ground and first floors, but only cracks in some of the infill walls. We heard from people in the neighbourhood that these buildings are going to be repaired. These buildings were around five years old, seemed well designed and built, and achieved the performance objective of life safety under 2% in 50-year demand.




Day 3 Continued: İslahiye - School Damage and Reconstruction, Interviewing the Young Survivors

The next stop was near station 2718 on the outskirts of İslahiye, near Kırıkçalı, which recorded a PGA of 0.65 g. The station was situated in a school compound constructed in 2014. The school building was completely damaged, but a replacement school was already being constructed next to it.




Next, we quickly stopped by station 3143 in the town of Akbez, once again located in a school compound, where we interviewed a few school kids about their experience of the earthquakes. The station recorded a PGA of 0.39 g. Just two buildings collapsed in the town, and the remaining buildings have slight to no damage.



Day 3 Continued: Hassa - Swift Clean-up Amid Heavily Damaged District

From Akbez, we travelled to the nearby town of Hassa, close to station 3138, notable for the extremely high PGV of 215 cm/s recorded during the first Mw 7.8 earthquake. The town and district of Hassa were heavily damaged. Over one thousand buildings collapsed in the district, which had a population of 50,000 in 2022. The clean-up has been faster than in other places. The remaining mid-rise mixed commercial-residential buildings were almost all moderately damaged with interior walls completely gone, and had been evacuated. Low-rise residential, commercial, and mixed residential-commercial buildings, both RC and unreinforced masonry (URM), were less damaged overall, and many were still occupied at the time of our visit. However, it was difficult to get a sense of the complete picture, as the collapsed and heavily damaged buildings were already cleared from the scene.



Day 3 Continued: Kırıkhan - Mid-Rise Buildings Bear the Brunt

Next, we visited the town of Kırıkhan in Hatay province, where station 3142 recorded a PGA of 0.75 g. Once again, the station is located in a school compound. The school is a single-storey structure - we were unable to determine easily if the school building was reinforced concrete or masonry, but there was practically no damage to the school at all other than a few hairline cracks.

 

The mid-rise buildings in Kırıkhan seem to have borne the brunt of this earthquake sequence. We saw a similar pattern here, as with many of the towns visited previously, with the low-rise buildings mostly unscathed, but the 6-8 storey apartment buildings with moderate damage or higher. A couple of resident families who had had to evacuate their apartments due to interior damage were kind enough to let us enter their apartments to see the damage from within.






Day 4: Antakya's Seismic Divide - East vs. West of the Orontes River

The fourth day was spent in the province of Hatay, one of the most affected provinces, and mostly in the city of Antakya. This city is located on the banks of the Orontes River. East of the river the city is composed mainly by a mix of reinforced concrete and masonry single-family 1-3 storey buildings. West of the river the city mostly comprises dense neighbourhoods of 7-12 storey multi-family residential buildings built in the last decade. Most of the multi-family residential buildings were heavily damaged and slated for demolition, collapsed, already demolished, or in the process of being demolished. Large parts of the city were uninhabitable at the time of our visit.



Day 4 Continued: Antakya - Tragic Site of Rönesans Rezidans

We visited the site of the erstwhile Rönesans Rezidans,  where 750 people died in a single luxury apartment building. The site had been completely cleaned up by the time of our visit.



Day 4 Continued: Unforeseen Resilience - Hatay Fenerbahçe School

The survey team visited three of the five AFAD seismic stations located within the city limits of Antakya. The first one was station 3129 in the Turunçlu neighbourhood in Defne district, on the outskirts of Antakya. The station recorded a PGA of 1.4 g and PGV of 171.5 cm/s. In the vicinity of this station, there were mostly 4–5 storey multi-family residential buildings that suffered extensive damage or collapse. Those that were still standing were uninhibited since even if the structural members had no visible damage, the partition walls were severely damaged and some occupants had also broken down external walls to retrieve their belongings.




The second location was the Hatay Fenerbahçe primary school, which housed station 3131. This station recorded a PGA of 0.37 g in the first earthquake. The school and station are located on hard rock at an elevation of around 150 m above the river. The three-storey school had practically no signs of damage, and neither did any of the low-rise single-family residential houses (a mix of reinforced concrete and unreinforced rubble stone masonry houses) which was rather surprising.



Day 4 Continued: Antakya - Assessing Damage Near the River

The final location we surveyed in the city of Antakya was station 3123 in the General Şükrü Kanatlı neighbourhood. This location is very close to the river, on the west bank, and recorded a PGA of 0.67 g and PGV of 188.8 cm/s. The surroundings of this station mostly consisted of 5–7 storey moment frame reinforced concrete buildings multi-family residential or mixed commercial-residential buildings were extensively damaged, with several collapses.




Final Day: İskenderun and Osmaniye - Liquefaction and Building Response

The last day of the mission was mostly spent in the port city of İskenderun in Hatay province, and the city of Osmaniye in Osmaniye province. In İskenderun, several signs of soil liquefaction could be observed along the promenade and the subsidence due to lateral spreading even led to the collapse of a few tall buildings. We surveyed a few buildings in the vicinity of station 3112, which is located on the coast at sea level, and recorded a PGA of 0.17 g in the N-S direction. Low-rise residential buildings along the promenade generally had very little damage. In the debris from one of the older low-rise buildings that had collapsed, the rebar appeared to be non-corrugated and rusted. Taller buildings had more visible signs of damage.



Finally, in Osmaniye, we stopped at station 8003, which recorded a PGA of 0.18 g in the first earthquake. While we observed damage to the mid-rise structures and also some collapses, the low-rise buildings had practically no damage.



 

General Observations: Insights and Conclusions


 

Following are some general observations from the survey:

 

Mid-Rise vs. Low-Rise Buildings

  • We observed only slight damage (or even no damage in some cases) to the 1-2 storey RC MRF single-family residential buildings, even at sites with very high shaking.

  • A substantial fraction of the 6-7 storey RC MRF with infill walls, multi-family residential structures had at least moderate damage, with all infill walls heavily damaged, and most of these buildings had been evacuated.

  • Low-rise buildings suffered less damage in comparison to the mid-rise buildings which seem to have borne the brunt of this earthquake sequence.

 

Performance of School Buildings

  • The schools we visited (typically the locations of many of the seismic stations in our itinerary) generally had very low damage.

 

Impact of Design Regulations

  • Performance objectives like life safety under 2% in 50-year loads can still lead to massive population displacement as many of the buildings that satisfied this performance objective did not collapse but are now evacuated.

 

Assessing Post-Disaster Building Characteristics

  • Since we came in four months after the events, we were generally not able to observe the characteristics of the buildings that collapsed or the ones that suffered heavy damage and that had already been demolished. The mid-rise multi-family residential buildings we observed were mostly constructed post-2000. The low-rise buildings we observed, on the other hand, had a broader mix of construction ages.

 

Calibrating Vulnerability Models and Informing Future Regulations

  • The data collected in the course of the mission will allow us to better constrain and calibrate the vulnerability models and therefore improve our estimates of earthquake risk. Field data is also useful for understanding the impact of design regulations on the performance of the built environment and in the improvement of future regulations.

 

 

Acknowledgements:

We would like to extend our sincere thanks to USAID-BHA for supporting this mission, to Kishor Jaiswal (USGS) for his tireless efforts in leading the damage survey, and to all of our colleagues from KOERI, METU, and Hacettepe University for sharing their expertise and knowledge with us during the mission.

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