Seismic site characterization in Gaziantep, Türkiye using SPT and MASW techniques

This paper presents an assessment for the seismic site characterization (SSC) in Gaziantep province located in southern central Türkiye, severely affected by three earthquakes of 7.7 Mw occurred in Pazarcik (Kahramanmaras) on February 6, 2023, 7.6 Mw occurred in Elbistan (Kahramanmaras) on February 6, 2023, and 6.4 Mw occurred in Defne (Hatay) on February 20, 2023, which claimed more than 55.000 lives. Data from 204 boreholes including Standard Penetration Test- N value (SPT-N) and Rock Quality Designation (RQD) values, and from 120 Multichannel Analysis of Surface Wave (MASW) tests conducted in the same area was analyzed by maps generated using a GIS software with Inverse Distance Weighing (IDW) feature applied for spatial interpolation. In majority of the study area, the SPT-N values were found to be greater than 15, and the Ground Water Table (GWT) level was deep enough (>15m) not to impact the engineering parameters, whilst, RQD values predominantly between 25 % and 50 % pointed out poor to very poor quality. Based on the National Earthquake Hazard Reduction Program (NEHRP) provisions, major part of the study area falls under class B and C. Furthermore, empirical correlations were derived among the values of SPT-N and V_s30 in order to characterize the geotechnical properties in an area where soil characteristics change significantly over a short distance, thereby helping the researchers and practitioners working on the earthquake resistant structures across the world.