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.

As a potential source of damage, earthquake-induced liquefaction is a major concern for embankment safety and serviceability. Densification has been a popular method for improving the performance of liquefiable soils. Understanding embankment settlement mechanisms plays a fundamental role in determining densification remediation. In this work, nonlinear dynamic analysis of embankments on liquefiable soils is conducted by the finite-difference program FLAC3D (version 6.0) with the simple anisotropic sand constitutive model. Numerical models are validated via dynamic centrifuge test results reported in the literature. The effects of densification countermeasures on the mean and differential settlements are explored in this study. Furthermore, the effects of the densification spacing and width are investigated to optimize the geometry of the densified regions. The development of pore pressure and the movement of the surrounding loose soil are discussed. The results show that both the mean settlement and differential settlement should be simultaneously utilized to comprehensively assess the overall effectiveness of densification treatment. The mean settlement is influenced by the densification spacing and width, but the differential settlement is highly associated with the inner edge of the densified region. This study provides insight for improving the design of the location and lateral extent of densification regions to prevent excessive embankment settlement.

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.

Local site conditions recognized as a determining factor in assessing the extent of seismic hazard and damage distribution during earthquakes. Present study emphasizes seismic hazard of international business corridor of Agartala town capital of Tripura, one of the northeastern state of India categorized as highest seismic zone (zone V) attributing seismic response of local subsoil deposits under site-specific scenario earthquake motions including liquefaction susceptibility prediction. One-dimensional nonlinear ground response analysis with input of geotechnical parameters was carried using DEEPSOIL (2018) program across central zone of Agartala city and liquefaction susceptibility analysis are performed based on standard penetration test (SPT) utilizing well-established empirical relationship. The novelty of results lies in use of site-specific dynamic parameters of subsoil and synthetic ground motions based on scenario earthquake. Besides, numerical model was validated with a recent past liquefaction case study in Tripura which also attributes key highlight of this study. Key seismic hazard parameters in the form of peak ground acceleration (PGA), amplification factor (Af), and predominant frequencies (fn) are presented through geographical information based spatial maps. These maps provide crucial inputs for planners and designers for future urban planning along with seismic strengthening of existing infrastructures. This comprehensive approach offers new perspectives on seismic hazard assessment and future management plan in this region.

At 4:17 am (1:17 UTC) on Feb. 6, 2023, an earthquake with Mw=7.8 struck near Pazarc & imath;k City in south-central Turkey, followed by a 7.5 Mw event about 9 h later. The subsequent earthquakes can cause severe damage which might not be the case for single earthquakes. In this study, a series of shake table tests on level ground with a sloping base model were conducted to investigate the effects of subsequent liquefactions on two 2 x 2 pile groups with a minor fixity in the caps. Adequate time intervals for complete dissipation of excess pore water pressure in the liquefiable layer were permitted at the end of each shaking. For this purpose, the free field soil and the piles were sufficiently instrumented to measure various parameters during and after the shakings. In this paper, the results of one of the shakings are reported and discussed in detail, and the results of other shakings are compared. The reported results contain time histories of acceleration, displacement, pore water pressure, bending moment, shear force, and lateral pressure on the piles. The ground settlements due to subsequent earthquakes are also measured and reported. The findings reveal that in a level ground liquefiable layer overlying a sloping base, lateral spreading may also occur and affect the piles behaviour especially in subsequent earthquakes. In addition, a practical relationship is proposed from the experimental results to estimate the residual shear strength of the liquefied soil.

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 seismic response of cable-stayed bridges is characterised by complicated interactions between the deck and the towers. These are influenced by the possible damage in the structure, and also by design choices or constraints such as the tower shape, the span, the cable arrangements, the support conditions and the type of foundation soil. The aim of this work is to assess the influence of these effects on the seismic behaviour of a large number of cable-stayed bridge finite element models. The results of the nonlinear dynamic analyses show the importance of the tower geometry. This is especially significant in short-span bridges with abrupt changes in the inclination of the lateral tower legs, which can lead to large levels of damage in the form of concrete cracking, reinforcement yielding and overall energy dissipation. Finally, design recommendations are proposed to improve the seismic response of the towers.

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.