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 (R_jb), and epicenter distance (R_epi)) in reflecting the actual damage status after the 2023 Kahramanmaraş 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 Türkiye (AFAD) stations (Gaziantep, Hatay, Kahramanmaraş, 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, R_jb-%14, f₀-%10, and R_epi-%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.

The focus of this study is to examine the soil properties and liquefaction potential of the Erenler center district in a critical tectonic zone that can produce large earthquakes, such as the North Anatolian Fault Zone (NAFZ). In this sense, 40 surface wave measurements and 52 geotechnical drillings were employed. Accordingly, the liquefaction potential index (LPI), liquefaction severity index (LSI), Ishihara boundary (IB) curve, and Ishihara-inspired index (LPI_ISH) liquefaction approaches from geotechnical and geophysical methods were used as integrated. All liquefaction analyses were examined for two scenarios, Mw: 7.4 1999 Izmit (a_max: 0.41 g) and Mw: 7.0 1967 (a_max: 0.28 g) Mudurnu. According to the analyses, almost all of the study area showed liquefaction risk in the Izmit scenario. In the Mudurnu scenario, liquefaction risk distribution decreased parallel to acceleration. The LPI, LPI_ISH, and IB liquefaction risk results for both scenarios support each other. On the other hand, it was determined that the probability of liquefaction was lower in the LSI evaluation. The spatial distribution of the liquefaction potential of the Vs-based and SPT-based LPI assessments had a similar pattern. These results show that the LPI approach, originally SPT-based, can also be calculated based on Vs. In addition, according to Vs₃₀-based (average shear wave velocity at 30 m depth) soil classification criteria, low-velocity character E and D soil groups dominate the Quaternary alluvial basin. This indicates that deformation-induced failures may occur even in areas with a low probability of liquefaction in similar strong ground motions. In addition, the evaluation of liquefaction with many approaches in two different bases within the scope of the study constitutes a novelty for the study area and liquefaction analyses. While performing diversified liquefaction analyses and approaches will contribute to obtaining more reliable soil liquefaction results, more case studies are needed to elucidate these comparisons.

Landslides following the development of slope instability can have serious consequences. Geophysical surveys have potential to aid in the understanding of landslides and their instability. This study described a landslide that occurred under particular geomorphological and meteorological conditions in Erenler (Sakarya, NW Türkiye) using electrical resistivity tomography (ERT) and multi‐channel analysis of surface waves (MASW) surveys and mechanical drillings. Data showed that the landslide is characterized by downslope movement of an altered clay unit over a claystone unit. The traditional landslide model used to interpret geoelectric data involves sliding of a relatively low‐resistivity material over higher resistivity bedrock. Here, the ERT survey showed a relatively high‐resistivity sliding material moving over relatively low‐resistivity bedrock units corresponding to the claystone unit. The relatively lower resistivity of the whole study area was related to the clay‐rich materials detected in the boreholes. This low‐resistivity unit was detected at high velocity in the MASW section, and it was understood that this layer was a compact structure acting like bedrock. The detected slip surfaces, landslide scars and slip surface toe indicate that the movement character of the landslide is retrogressive. The study results showed that the integrated and comparative use of different geophysical methods effectively reduces interpretation uncertainties and potential errors and leads to much better landslide characterization.

The strong ground motion effect is amplified or de-amplified due to the change in subsoil condition. Local soil properties prediction is critical for earthquake-safe areas and the earthquake hazard assessment of existing structures. This study was carried out with time-domain 1D Non-linear analysis to understand the soil response characteristics of the Arifiye district. In this sense, geotechnical drilling at 47 points and surface wave analysis at 44 points were performed. Site response profiles in the study area were analyzed with the DeepSoil program for M_w:7.0 1967 Mudurnu and M_w:7.4 1999 Kocaeli earthquake scenarios. Peak spectral acceleration (Pga) and spectral acceleration (Sa) values were determined in the analysis of the Mudunu scenario as 0,11-0,24 g and 0,44-1 g, respectively. The Kocaeli scenario's Pga and Sa distribution were obtained in a wide range of 0.2-0.56 g and 0.47-2.3 g, respectively, compared to the Mudurnu scenario. Especially in the M_w:7.4 model, high Pga (>0.3g) and Sa (>1g) values were obtained in the uncemented units located north of the study area. Kocaeli scenario results showed that the spectral accelerations at the surface in soil groups D and E were higher than the Turkish Building Earthquake Code (TBEC) building requirements, and it is necessary to update the earthquake design spectra site-specific. On the other hand, it can be said that the southwest of the study area is safer and more suitable residential versus throughout the study area. The results clearly showed the effect of ground conditions and strong ground motion selection on earthquake-resistant building design.