On 6 February 2023, two independent earthquake pairs on the East Anatolian Fault Zone, with epicenters in Pazarcık (Mw = 7.7) and Elbistan (Mw = 7.6) districts of Kahramanmaraş province, caused great destruction. Adıyaman and Gölbaşı districts of this city are among the settlements most affected by the earthquake. Especially in the district where geotechnical damages are most observed, the destructive effects of earthquakes have been clearly observed in buildings with different structural systems. In this study, information is given about the earthquakes that hit the region and the fault zone where the earthquakes occur. Geotechnical and structural damages occurring in the villages and center of the district were evaluated within the scope of earthquakes and structural engineering. It can be stated that damages observed in the district center are generally caused by soil–structure interaction problems. The fact that masonry structures, which are widely used in rural areas, do not benefit from any engineering services has an impact on the level of damage. The main reason for the damages occurring in the reinforced concrete structures in the district is the reinforced concrete system that is not designed properly or not built in accordance with the design. This case study demonstrated the importance of earthquake–soil–structure interactions in line with earthquake-resistant building design principles.

The Cameli Basin and its surroundings are located in southwestern Anatolia, Türkiye, and are one of the tectonically active regions in western Türkiye. The Curie point depth of continental crust can help us to determine the regional tectonic and geothermal structures. The aeromagnetic magnetic data of the study region were used to determine the Curie Point Depth estimates. The fractal-based centroid method is used for this purpose. The fractal approach removes the effect of fractal magnetization in the power spectrum. The depth to the bottom of the deepest magnetic sources in the study region ranges between 6.9 and 14.05. The estimated thermal gradient varies from 41.28°C/km to 89.23°C/km and the average value is 58.59°C/km (580°C for magnetite). The distributions of earthquakes are compatible with NW-SE trending estimated Curie depth anomalies. Interpretation indicates that the depth to the Curie isotherm is considerably shallower than the Moho depth.

In this study, a statistical analysis of regional and time-dependent changes of earthquake activity in Bodrum and its vicinity before the Bodrum-Kos earthquake (Mw 6.6) that occurred on 21 July 2017 was performed and the Gutenberg-Richter b-value change was investigated. The earthquake catalog used in the calculations was taken from Boğaziçi University, Kandilli Observatory and Earthquake Research Institute. This catalog contains 16947 earthquakes with M>2 between 2004 and the time until the Bodrum-Kos earthquake of 21.07.2017. The completeness magnitude for these earthquakes was calculated as 2.6. The b-value was calculated as 1.25 ±0.01 using the maximum probability method. Considering that tectonic earthquakes have b-values between 0.5-1.5, it is seen that the b-value obtained by Gutenberg-Richter law for the vicinity of Bodrum in this study is a good fit. In addition, it was observed that b-value took high values in the north of Bodrum before the Bodrum-Kos earthquake occurred. Low values are observed in the southeast of Bodrum. Stress accumulation was correlated with b-values for the region.

In this study, measurements obtained through the first two profiles from the TÜBİTAK (The Scientific and Technological Research Council of Turkey) project titled “Research of the Crustal Structure of Northwestern Anatolia with Geophysical Methods” from 2007 were used. Magnetotelluric (MT) measurements were taken from 174 sites approximately every 3 km in the region between Zonguldak and Akşehir (Konya). Dimensionality analysis was conducted with the decomposition of the impedance tensor obtained through the measurement data from the two profiles. The relationship between the observed geo-electric behaviors, the geological structure of the area and the MT dimensionality changes were detected. Two-dimensional (2D) and three-dimensional (3D) structures were revealed as a result of the dimensionality analysis obtained through the MT data from the region located between Zonguldak and Akşehir. The dimensionality was observed to be complex in small periods due to the heterogeneous conductive materials close to the surface and 3D structures were observed to be predominant in high periods. Moreover, the dimensionality near the suture zones were observed to be more complex compared to other areas according to the dimensionality analysis results. The structures in the vicinity of the North Anatolian Fault were found out to be N-NE striking. This indicates the accuracy and reliability of the results.

B value analysis obtained using earthquake catalogues has been associated with stress accumulation for a very long time. In this study, the spatial and temporal distribution of the b value, also known as the frequency magnitude distribution factor, was calculated and examined before and after the February 6, 2023, Kahramanmaraş earthquakes (Mw7.7 and Mw7.6). For this, all earthquakes that occurred between 1900 and the earthquakes of February 6, 2023, and all aftershocks that occurred until September 1, 2023, were used. A circular area with a radius of 300 km, including nearby active faults from the center of the first earthquake to the center of the second earthquake, was divided into grids of equal size. The b value was calculated for each grid using the maximum likelihood method. Very low b values were detected in the area where the first earthquake occurred, and it was observed that the b value decreased relatively in the area where the second earthquake occurred. From the change in b value over time, it was determined that the b value has decreased significantly in recent years. This situation is associated with stress accumulation in the area where both earthquakes occurred, especially the low b values of the region where the first earthquake occurred. The fact that b values obtained using aftershocks are still low is evidence that the tension in the region has not been completely relieved and aftershocks will continue for a long time. At the same time, as a result of this study, the low b value was considered as a precursor to major earthquakes.