Evaluating Seismic Site Response in a Deep Alluvial Basin: The Case of the Bornova Basin (Izmir)

Authors : Hüseyin Akkuş, Nihat Sinan Işık

Pages : 1617-1630

Doi:10.29109/gujsc.1836506

View : 122 | Download : 140

Publication Date : 2025-12-25

Article Type : Research Paper

Abstract :This research investigates the effects of deep alluvial basins in the Bornova region of Izmir on earthquake ground motion by combining field characterization with 1D and 2D equivalent linear soil response analyzes. In the study, soil-bedrock interfaces were modeled using two idealized two-dimensional geological sections representing the Bornova Basin. The study area has a geological environment characterized by east-west trending normal faults along the Inner Izmir Bay and covered by sedimentary units. Borehole data indicate the presence of heterogeneous geological units consisting of clay, silt, sand, and gravel in some areas. The Spatial Autocorrelation (SPAC) method indicates that, in the west, the alluvial units with low shear-wave velocities become thicker with depth, whereas in the east, shear-wave velocities increase from the surface downward. In the analysis, the shear modulus reduction and damping-ratio curves obtained from laboratory experiments were compared with widely used reference curves in the literature, and the most suitable curves were used in the analysis. The analysis used three different recordings: the 1999 Duzce earthquake record, the 30 October 2020 Samos earthquake record, and a superposition of Gabor pulse compatible with the target spectrum. The 2D analysis shows higher spectral acceleration values compared to the 1D analyses, and hip enlargement is concentrated in the ~0.3, 1.0, and 1.6 s period range. This situation aligns with the damage distribution observed during the 2020 Samos earthquake (Mw 6.6), indicating that basin effects in Bornova were decisive during the earthquake.
Keywords : Bornova Baseni, Saha Tepkisi, Basen Etkileri, Dinamik Analiz

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