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- BildiriYalnız künye2026Scopus SJRQ4Residual-Based Evaluation of Basin and Basin Edge Effects in Türkiye: Implications for Regional Site Amplification Modeling
İçen, Abdullah; Ilki, A.; Goksu, C.; Cinar, T.; Erdik, M.
This study investigates basin, basin edge and complex topography effects in ground motion records using residuals from empirical ground motion models, to better understand regional site amplification patterns in Türkiye. Using data from the updated Strong Motion Database of Türkiye (SMD-TR) strong-motion database, we compute residuals using site amplification function and analyze their spatial distribution across regions. The clustering technique, Gaussian Mixture Models (GMM), is employed to identify regions with coherent residual patterns, primarily to capture regional site effects. After regionalization, peak amplifications within the VS30 range of 400–550 m/s are examined for potential associations with sedimentary basins or basin edge effects. The results reveal systematic amplification anomalies within the VS30 range of 400–550 m/s that are not fully captured by conventional site proxies such as VS30. Notably, residuals consistently cluster along basin edges and within deep valley regions, indicating the influence of complex three-dimensional and topographic amplification mechanisms. These observations underscore the limitations of current site characterization approaches and motivate further refinement of site response models, particularly for partially non-ergodic applications in seismic hazard analysis. This study focuses on residual-based evaluations to identify potential basin, basin-edge, and topographic effects that warrant more detailed investigation.
- MakaleYalnız künye2026Scopus SJRQ1Regionalized Bayesian site amplification models for Türkiye
İçen, Abdullah
Accurate representation of site amplification is essential for seismic hazard analysis, particularly in regions with complex geological structure. This study develops a Bayesian hierarchical site amplification model that captures nonlinear, period-dependent, and regionally variable behavior using an extensive strong-motion dataset from Türkiye. The model employs a piecewise VS30 functional form derived from nonparametric scaling and clustering, and incorporates nonlinear scaling with reference rock motion intensity (PSArock). Regional variability is introduced through random-slope adjustments, enabling spatial differences in amplification to be represented while maintaining statistical stability through partial pooling. Results indicate pronounced nonlinear and regional variability for soft soils and reduced regional differences for stiff sites (VS30 > 600 m/s). A key observation is a systematic amplification peak within the 400–550 m/s velocity range, where the model exhibits consistent underprediction across periods. Because this feature persisted even for stations located on flat basin interiors, a detailed investigation of stations in this VS30 interval was conducted and is presented in the study. Mapping and site-specific examination reveal that many of these stations are located near slope breaks, basin edges, or transitional geological settings, suggesting that 2D/3D wave-propagation or impedance-transition effects—rather than VS30 alone—may drive the increase in the amplification. Additionally, residual underprediction persists at high-VS30 rock sites, highlighting the need for improved empirical characterization of stiff-soil and rock conditions. Overall, the proposed Bayesian framework provides a flexible, data-driven, and uncertainty-aware approach for modeling site amplification, with direct applications in probabilistic seismic hazard analysis and performance-based earthquake engineering.
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İncele - MakaleAçık Erişim2024Scopus SJRQ1Local site effects at the selected stations affected by the February 6 2023 Türkiye Earthquake Sequences
Ilhan, Okan; Indır, Onur; Muratoğlu, Gamze; İçen, Abdullah; Albayrak, Kubilay; Sandıkkaya, M. Abdullah; Askan, Ayşegül; Arduino, Pedro; Taciroğlu, Ertuğrul
This paper explores the applicability of one-dimensional (1D) nonlinear (NL) and equivalent-linear (EL) site response analyses (SRA) for characterizing site effects at selected strong ground motion stations impacted by the February 6, 2023 Türkiye earthquakes. The 1D NL simulations generally underestimate site response at softer sites and for long periods likely due to basin effects and the uncertainties associated with site properties and the 1D approximation. The inclusion of the high-frequency spectral decay parameter (κ0) in 1D simulations decreases the prediction bias of nonlinear SRA, especially at soft sites for short periods. Moreover, the theoretical transfer functions (TTFs) are demonstrated to capture the fundamental site period through in horizontal-to-spectral vertical ratio (HVSR) using ground motion data before and after the February 6, 2023 main event.
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