EVALUATION OF SITE EFFECTS IN KAHRAMANMARAS EARTHQUAKES REGION BY CHARACTERIZATION OF SGM STATIONS

To reliably interpret the ground motion data obtained from strong ground motion stations, the local soil conditions (i.e., shear wave velocity, fundamental period, site class) must be known at the time of the earthquake. Hence, the response of the local site effects (i.e., site amplification due to the basin, topographic effects, directivity, pulse) to uncertainties that occur during the earthquake can be evaluated more accurately. Otherwise, uncertainties may arise regarding the reliability of the results. On the 6th of February 2023, the Mw 7.7 Pazarcik and Mw 7.6 Elbistan of the Kahramanmaras earthquakes drastically hit southeastern Turkiye. As a result of this successive series of earthquakes, intensive damage occurred to buildings and infrastructure and, unfortunately, caused many casualties. The earthquakes experienced affected many provinces, particularly Kahramanmaras, Adiyaman, Hatay, and Gaziantep. Following these earthquakes, when the records obtained from the AFAD Turkish Accelerometric Database and Analysis System (TADAS) database in the region were examined, it was observed that the maximum PGA distributions reached very high values during both earthquakes, and uncertainties concerning the local site conditions were encountered. The accuracy of these records was questioned due to the very high acceleration of recordings (i.e., Pazarcik and Hassa station). The earthquake might have altered the local site conditions and crustal structure where these stations are deployed. This effect has been observed to be particularly significant in locations with soft soil sediments of alluvium and might have impacted the acceleration recordings. Within the scope of this study, shear wave velocities and corresponding site classes at these stations have been characterized after the earthquakes via surface seismic methods using the active Multichannel Analysis of Surface Wave (MASW) and the passive Microtremor Array Method (MAM). The results were synthesized together, and deep Vs profiles of the stations were generated. Considering the site classification of the Turkish seismic design code, the soil characteristics of the stations and the local site effects have been evaluated. Site characterization of the stations that recorded the Kahramanmaras earthquakes is expected to provide predictions to model the uncertainties of site response considering the local site effects.