On February 6, 2023, two devastating seismic events, the Kahramanmaras, earthquakes, struck the Eastern Anatolian Fault Line (EAF) at 9-h intervals. The first earthquake, with a moment magnitude (Mw) of 7.7, struck the Pazarc & imath;k district, followed by a second earthquake with a moment magnitude (Mw) of 7.6 in the Elbistan district, both within the Kahramanmaras, province. These dual earthquakes directly impacted eleven provinces in Eastern and Southeastern Anatolia leading to significant loss of life and extensive damage to property and infrastructure. This study focuses on revealing the main parameters causing to the collapse of reinforced concrete (RC) buildings by examining their compliance with legislation and earthquake codes in force at the time of construction. For this purpose, detailed examinations such as field observations, collection of general information and official documents about the buildings, determination of material properties and soil characteristics, and three-dimensional finite element (FE) analysis of 400 totally collapsed RC buildings in the Kahramanmaras,, Ad & imath;yaman, Hatay, and Gaziantep provinces, which were among the cities affected by the Kahramanmaras, earthquakes were performed. The findings of this study contribute to a better understanding of the seismic deficiencies of buildings in earthquake-prone regions and provide information on which strategies to develop to increase the resilience of buildings with similar characteristics in other earthquake regions against future seismic events. Considering that the time from the beginning of the construction of the building until its completion consists of several stages, it can be seen that 43.58 % of the errors that cause damage and collapse of the buildings in this study are made in the construction stage, 25.57 % in the FE analysis stage, 24.77 % in the license stage, and 6.07 % in the after construction stage. Thanks to the development process of earthquake codes, regulations in building inspection practices and easier access to quality materials have greatly reduced the damage and collapse of buildings constructed in recent years.

On February 6, 2023, two major earthquakes with magnitudes Mw = 7.7 and Mw = 7.6 struck southeastern Turkiye, causing catastrophic damage and loss of life across 11 provinces, including Malatya. This study focuses on documenting the geotechnical observations and structural damage in Dogansehir, one of the hardest-hit districts not only in Malatya but in the entire affected region. An overview of the-region's tectonic and geological background is presented, followed by an analysis of ground motion data specific to Malatya. A detailed examination of seismic data from stations near Dogansehir was provided to better understand the seismic demands during the earthquakes. The paper then provides insights into the geotechnical conditions, building characteristics, and a damage ratio map of Dogansehir. The influence of local tectonics and geology on the observed damage is analyzed, alongside an evaluation of the seismic performance of masonry and reinforced concrete structures. Dogansehir, located near the epicenters of the Kahramanmaras earthquakes, suffered major structural damage. This was due to the surface rupture occurring near the settlement areas, the establishment of the district centre on the alluvial soil layer and the deficiencies/errors in the building systems. Building settlements on or near active fault zones, as well as on soft soil, leads to serious consequences and should be avoided or require special precautions.

Two earthquakes, Mw = 7.8 Kahramanmaras,-Pazarcik, and Mw = 7.6 Elbistan, occurred on February 6, 2023, approximately 9 h apart. These earthquakes caused devastating effects in a total of 11 nearby cities on the east side of T & uuml;rkiye (Adana, Adiyaman, Diyarbakir, Elazig, Gaziantep, Hatay, Kahramanmaras,, Kilis, Malatya, Osmaniye, and S,anliurfa) and the north side of Syria. These earthquakes provided an outstanding prospect to observe the effects of liquefaction in silty sand and liquefaction-like behavior in clays (cyclic softening) on the stability of structures. This paper specifically presents the post-earthquake reconnaissance at three sites and evaluations of four buildings within these sites in Adiyaman Province, Golbas, i District. First, important role of post-earthquake piezocone penetration test (CPTu) in characterizing the subsurface conditions was presented. Then, the effect of soil liquefaction and cyclic softening on the performance of four buildings during the earthquakes was evaluated. These structures represent the typical new reinforced concrete buildings in T & uuml;rkiye with 3 to 6-story, situated on shallow (raft) foundations, and demonstrated diverse structural performances from full resilience to moderate and extensive damage during the aforementioned earthquakes. Based on the interim findings from these sites, the potential factors that caused moderate to severe damage to buildings were inspected, and preliminary-immediate insights were presented on the relationship between structural design, soil properties, and the performance of buildings with shallow foundations.

The impact of site effects on ground motion is a critical factor for earthquake disaster prevention and mitigation, as these effects can amplify ground motion and affect building fragility. On February 6, 2023, southeastern Turkey was struck by two strong earthquakes, with magnitudes of Mw7.7 and Mw7.6, followed by numerous aftershocks. These events resulted in severe casualties and substantial economic losses. Field investigations revealed severe damage to mid-rise and high-rise buildings in Kahramanmara & scedil; and Antakya. Both cities are located in valley regions, which are particularly susceptible to earthquake damage due to the amplification of ground motion caused by soft soil conditions and valley topography. In this paper, Horizontal-to-Vertical Spectral Ratio (H/V) technique is used to decipher how site effects affect ground motion and damage using the strong motion records. The analysis revealed that the predominant frequency of ground motion decreases near the valley areas and increases toward the hill slopes. These spatial variations in predominant frequency have significant implications for building safety. Structures located in areas where the predominant frequency matches their natural frequency are more prone to resonance effects, significantly increasing the risk of damage during seismic events. Additionally, the study found that the nonlinearity of the site conditions amplified the acceleration response spectrum at a period of 1 s. This amplification exceeded the local structural design capacity. The findings indicate that site effects can significantly intensify earthquake damage in Kahramanmara & scedil; and Antakya by amplifying ground motion and increasing the vulnerability of mid-rise and high-rise structures.

This paper has attempted to determine the weighting levels of the soil and ground motion parameters (engineering bedrock depth (EBd), average shear wave velocity (Vs30), fundamental frequency (f0), peak ground acceleration (PGA), Joyner-Boore distance (Rjb), and epicenter distance (Repi)) in reflecting the actual damage status after the 2023 Kahramanmara & scedil; earthquakes, which have a wide impact area of 11 provinces. The analytical hierarchy method (AHP), a multi-criteria decision-making (MCDM) process, was used to analyze these parameter data sets obtained from 44 Disaster and Emergency Management Presidency of T & uuml;rkiye (AFAD) stations (Gaziantep, Hatay, Kahramanmara & scedil;, and Osmaniye). The priority order of the parameters before the analysis was systematically collected. These parameters were categorized into soil, ground motion and earthquake source-path properties. Considering the literature, these characteristics and their combined effects were systematically weighted with AHP under five groups. According to the weighted groups in the scope of the study, the actual damage data can be determined with a minimum accuracy rate of 70% (Group 1). In comparison, the best performance evaluation was 82% (Group 5). The parameter order and weights in the actual damage data evaluation are suggested as EBd-%28, PGA-%24, Vs30-%19, Rjb-%14, f0-%10, and Repi-%5 considering the very high accuracy rate of Group 5. This suggested weighting allows the rapid and effective estimation of the damage distribution after a possible earthquake only with soil, ground motion and earthquake source-path characteristics, even in cases where reliable structure data cannot be obtained.

T & uuml;rkiye has a history full of devastating earthquakes from past to present. The February 6, 2023, earthquakes in Kahramanmaras, Pazarc & imath;k and Elbistan, with magnitudes of Mw 7.7 and Mw 7.6, were among the most destructive in recent history, impacting 11 provinces and causing severe structural damage, especially in regions close to the fault line. Within the scope of this study, the 400 reinforced concrete buildings that collapsed due to the 2023 Kahramanmaras, earthquakes in the provinces of Kahramanmaras,, Ad & imath;yaman, Hatay, Gaziantep were examined in terms of seismic codes and soil conditions. The evolution of the Codes on Buildings to be Built in Disaster Areas (1975 and 1997-8), Code on Buildings to be Built in Earthquake Zones (2007) to which the relevant reinforced concrete buildings are subject, and T & uuml;rkiye Building Earthquake Code (2018) were discussed. The differences between the local soil conditions in these codes were revealed and it was evaluated how these local soil properties affect the seismic vulnerability of buildings. This study's findings highlight the critical role of the soil conditions on seismic vulnerability of buildings in earthquake-prone regions. They also offer valuable insights into developing strategies to enhance the structural resilience of similar buildings in other earthquake regions against future seismic events.

After two major earthquakes centred in Kahramanmara & scedil; on February 6, 2023, in T & uuml;rkiye, there was significant destruction of the building stock. More than fifty thousand people lost their lives, and many people lost their comfort of life even though they were rescued from the wreckage. Researchers have emphasized that this catastrophic consequence is generally caused by design and production errors and low material quality in almost all building types, especially reinforced concrete, steel, masonry, and prefabricated structures. Within the scope of this study, damage patterns and the design flaws of reinforced concrete structures in Malatya, which is one of the provinces affected by the Kahramanmara & scedil; earthquakes, were examined via a field study. During the fieldwork, it was determined that inadequate longitudinal reinforcement and stirrup reinforcement, in-depth reinforcement, and concrete quality, design errors in the column-beam junction area, ignoring the structure-soil interactions, short columns, torsional irregularity, and soft stories were the main factors that led reinforced concrete buildings to be heavily damaged or collapse. After the root causes of damage to reinforced concrete structures were examined, the measures and applications that should be taken to ensure that reinforced concrete structures can maintain their services in the event of earthquakes that are likely to occur in the future was discussed.

Seismically induced soil liquefaction was listed as one of the major causes of damage observed in the natural and built environment during the 2023 Turkiye-Kahramanmaras earthquake sequence. Reconnaissance field investigations were performed to collect perishable data and document the extent of damage immediately after the events. The sites with surface manifestations of seismic soil liquefaction in the form of soil ejecta, excessive foundation and ground deformations were identified and documented. The deformations were mapped, and samples from ejecta were retrieved. The ejecta samples were predominantly classified as sands with varying degrees of fines. Laboratory test results performed on liquefied soil ejecta revealed that the fines-containing liquefied ejecta samples are mostly classified as low plasticity clays (CL). Most of CL soil type ejecta were retrieved from Golbasi-Adiyaman region. The liquid limits of these samples varied in between 32 and 38%, their plasticity index values were estimated in the range of 16-23%. Surprisingly, two ejecta samples with plasticity indices higher than 30% were retrieved from Hatay airport, one of which was classified as high plasticity clay (CH). The majority of the fine-grained ejecta samples fall either on Zone B: Testing Recommended region of the Seed et al. (Keynote presentation, 26th Annual ASCE Los Angeles Geotechnical Spring Seminar, Long Beach, CA, 2003) susceptibility chart. Moreover, 12 out of 74 samples fall outside the susceptible limits defined by Seed et. These preliminary results suggest that clayey soils can produce liquefied ejecta when subjected to cyclic loading. Detailed site investigation and laboratory testing programs are ongoing to further investigate this rather unexpected response. Until their findings become available, the liquefaction susceptibility of silty-clayey soils' mixtures is recommended to be assessed conservatively with caution.

The 6 February 2023 Kahramanmara & scedil;-T & uuml;rkiye earthquake sequence (M7.8 and M7.6) presents an exceptional opportunity to investigate both the effects of local soil conditions on damage patterns under strong shaking conditions and the performance of building foundations in areas that experienced ground failure. The significant ground failure and structural damage in Ad & imath;yaman-G & ouml;lba & scedil;& imath; triggered an intensive series of detailed reconnaissance and field surveys. This article aims to present the resulting database of observations on ground failures, building, and foundation performances. The field reconnaissance of ground failures and their effects on building performances involved aerial and walk-down surveys, including high-quality photographs taken across the town. In addition, data on building damage statistics compiled by the Ministry of Environment, Urbanization, and Climate Change were accessed and analyzed. The subsurface characteristics of the town were characterized using available data from pre-earthquake site investigation campaigns employed for town planning purposes. It is concluded that the ground failures in the town primarily resulted from soil liquefaction and cyclic softening. Most of the poor building and foundation performances and ground failures were documented in the northern part of Atat & uuml;rk Boulevard, closer to the lake of G & ouml;lba & scedil;& imath;, where soil site characteristics were unfavorable. This revealed once again the significant effects of local soil site conditions, particularly soil liquefaction, on the intensified ground failures, foundation, and structural damage levels.

An earthquake event with a moment magnitude of 7.7 took place in Pazarc & imath;k (Kahramanmara & scedil;, T & uuml;rkiye) on February 6, 2023. Approximately 9 hours after this event, another powerful earthquake event in Elbistan (Kahramanmara & scedil;) with a moment magnitude of 7.6 occurred. This study reports the level of devastation in Kahramanmara & scedil;, Hatay, and Ad & imath;yaman cities of T & uuml;rkiye that were heavily affected. Mainly, the characteristics of the recorded input motions at the affected areas and their spectral accelerations at different sites (possessing different soil classes) along with the design values are evaluated. Moreover, soft-weak story failures and pancake collapses of buildings are discussed together with strong column-weak beam philosophy. The influence of site effect on the input motions and, therefore, on the structural damages is highlighted, too.