This paper presents the findings of field observations conducted in the aftermath of the earthquakes that struck the Pazarcik (Mw7.7) and Elbistan (Mw7.6) in Kahramanmaras province, Turkey on February 6th, 2023. The earthquakes, occurring on the East Anatolian Fault Zone (EAFZ), resulted in more than 50,000 losses of life and damage of more than 1.5 million properties across 11 provinces in Turkey. Field observations presented herein encompass seismological and strong ground motion data, geotechnical observations, as well as damage assessments of underground and above ground structures in various provinces and districts. The types and reasons of the structural damages were discussed. The study also examined the effects of high acceleration values and distribution of strong ground motions on the performance of structures. Soil liquefaction problems were observed in many locations such as Golbasi and Iskenderun. The paper highlights the geology, tectonics, strong motion characteristics, surface deformations, geotechnical and structural aspects, and the evaluation of lifelines in the affected area. Furthermore, the authors provide initial recommendations for improving disaster management, evaluating building stock, prioritizing urban transformation, strengthening infrastructure systems, addressing soil-building interaction issues, ensuring security measures during search and rescue efforts, utilizing satellite imagery effectively, considering seismic effects on water infrastructure, and taking a holistic approach to earthquake effects in industrial facilities.

Local site conditions may pose a significant influence on the seismic responses of submarine pipelines by altering both the offshore motion propagation and soil-structure interaction (SSI). This paper aims to provide an in-depth understanding of the influence regularity of local site conditions on the seismic performance of free-spanning submarine pipelines (FSSPs). For this purpose, a suite of underwater shaking table tests were performed to investigate the seismic responses of FSSP subjected to the offshore spatial motions at three site categories. Response comparison factor (chi R.ij${\chi }_{R.ij}$) is defined to quantify the structural response discrepancies caused by the seismic inputs at different sites. The test results indicate that responses of the studied model FSSP gradually increase as spatial offshore motions at softer soil sites are employed as inputs; and the values of chi R.ij${\chi }_{R.ij}$ vary with a maximum magnitude of up to 40%-60% for different response indices when the site soil changes from fine sand to clay. Subsequently, the corresponding numerical simulations are carried out to reproduce the seismic responses of the test model. The experimental and numerical results meet a good agreement, indicating that the developed numerical modeling method can accurately predict the seismic responses of FSSPs. Following this verified modeling method and using the p-y approach to address the SSI effect, fragility surfaces of the studied FSSP are derived in terms of PGA and site parameter VS30${V}_{S30}$ (shear-wave velocity in the top 30 m of the soil profile) via probabilistic seismic demand analyses. The impact of local site conditions on the seismic performance of the FSSP is quantitatively examined by comparing the fragility curves corresponding to various VS30${V}_{S30}$. Furthermore, a fast seismic damage assessment method is proposed for efficiently evaluating the performance of FSSPs buried in various offshore soil conditions. This approach proves beneficial for designers and decision-makers, enabling accurate estimation of seismic damage and facilitating the implementation of post-earthquake maintenance measures for FSSPs.