2-D and 3-D FE Modeling of Seismic Site-Basin Effects in Izmir-Bayrakli During October 30, 2020 M7 Samos-Aegean Sea Earthquake

Abstract During Samos-Aegean Sea Earthquake Mw=7.0, Turkiye-Izmir-Bayrakli district was affected the most due to deep-soft alluvial nature and the geometry of the basin, although the district is approximately 70 km away from the epicenter of the earthquake. In this study, seismic response of the Bayrakli basin, and the role of the soil stratigraphy and geometry on the recorded amplifications and prolonging of seismic shakings are investigated by using 1-, 2- and 3-D non-linear finite element-based dynamic response analyses. The idealized large-scale basin model is calibrated and validated by using available strong ground motion records, and the results of 1-D total stress-based equivalent linear site response analyses. The assessment results were presented in the form of spectral amplification, A(T), which was defined as the ratio of 3-D (or 2-D) soil basin spectral accelerations, normalized by reference rock spectral accelerations. A(T) was decomposed into the product of two independent amplification factors, namely A1D,Rock-Soil(T) and Asoil,1D-3D or 2D(T). A1D,Rock-Soil(T) represents the spectral amplification of a 1-D soil column as compared to that of a reference rock column (site), whereas Asoil,1D-3D or 2D(T) is soil amplifications estimated by a 3-D (or 2-D) model normalized by those of a 1-D model. The numerical simulation results were summarized in the form of A(T) and Asoil,1D-3D or 2D(T) contour maps, which suggest that the 3-D basin geometry-induced amplifications reach 1.4 and 1.6 in the E-W and N-S directions of the basin.