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<p>The Alborz seismic zone of northern Iran, home to the densely populated Tehran megacity, faces significant seismic risk due to active fault systems and limited strong-motion records. This study addresses this gap by analyzing accelerometric data from six earthquakes (M<sub>s</sub> 5.7–6.4, 1997–2010) recorded at 135 stations across the region. A classical single-station spectral inversion was applied to estimate source and path parameters for each record, using an initial grid search for the corner frequency followed by least-squares optimization. The mentioned methods characterize source parameters (corner frequency, stress drop, seismic moment), while path attenuation is quantified via shear-wave quality factor (Qs) and high-frequency kappa. Site-specific attenuation is evaluated using V<sub>s30</sub> (shear wave velocity for upper 30&#xa0;m soil). Key findings reveal: (1) kappa increases systematically with epicentral distance, confirming its path dependence, and exhibits an inverse correlation with V<sub>s30</sub> (lower kappa) in stiff soils, higher kappa in soft soils; (2) Q<sub>S</sub> values for the upper crust range 361–1072 (mean ≈577), reflecting regional attenuation heterogeneity; (3) Source parameters, validated against the Brune (J Geophys Res 75:4997–5009, 1970) model, show stress drops and rupture radii consistent with event magnitudes (M<sub>s</sub> 5.7–6.4). Observed-versus-simulated spectral errors remain ≤ 15% for critical parameters, affirming methodological robustness. Aggregated station-level results provide regional averages of Q<sub>S</sub>, kappa, and stress drop, critical for refining ground motion prediction equations.</p>

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Quantifying Source and Path Effects in the Alborz Region Through Earthquake Accelerogram Analysis

  • 期刊论文

  • 发表日期：

    2026年2月11日

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  • Sayeh Safavi,
  • Habib Rahimi

摘要

The Alborz seismic zone of northern Iran, home to the densely populated Tehran megacity, faces significant seismic risk due to active fault systems and limited strong-motion records. This study addresses this gap by analyzing accelerometric data from six earthquakes (Ms 5.7–6.4, 1997–2010) recorded at 135 stations across the region. A classical single-station spectral inversion was applied to estimate source and path parameters for each record, using an initial grid search for the corner frequency followed by least-squares optimization. The mentioned methods characterize source parameters (corner frequency, stress drop, seismic moment), while path attenuation is quantified via shear-wave quality factor (Qs) and high-frequency kappa. Site-specific attenuation is evaluated using Vs30 (shear wave velocity for upper 30 m soil). Key findings reveal: (1) kappa increases systematically with epicentral distance, confirming its path dependence, and exhibits an inverse correlation with Vs30 (lower kappa) in stiff soils, higher kappa in soft soils; (2) QS values for the upper crust range 361–1072 (mean ≈577), reflecting regional attenuation heterogeneity; (3) Source parameters, validated against the Brune (J Geophys Res 75:4997–5009, 1970) model, show stress drops and rupture radii consistent with event magnitudes (Ms 5.7–6.4). Observed-versus-simulated spectral errors remain ≤ 15% for critical parameters, affirming methodological robustness. Aggregated station-level results provide regional averages of QS, kappa, and stress drop, critical for refining ground motion prediction equations.