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<p>The seismic attenuation parameter, kappa (κ), is a critical factor in characterizing high-frequency ground motion and plays a vital role in seismic hazard assessment, ground motion prediction equation (GMPE) calibration, and site response modeling. This study investigates the spatial variability of κ in Northeast India, a tectonically active region at the convergence of the Himalayan orogeny and the Indo-Burmese arc, and examines the influence of geological and site conditions using 199 three-component seismic records from 115 earthquakes (M<sub>w</sub> 2.5–6.8) at epicentral distances up to 400&#xa0;km. κ was estimated using strong motion data from PESMOS and local broadband recordings from Mizoram, applying a modified Anderson and Hough (Bull Seismol Soc Am 74(5):1969-1993, 1984) approach with exponential decay fitting to the raw amplitude spectra. The analysis shows κ values ranging from 0.019—0.156&#xa0;s for the EW component, 0.013—0.134&#xa0;s for the NS component, and 0.005—0.120&#xa0;s for the vertical component, with higher attenuation at sites underlain by unconsolidated sediments and alluvium with average κ values between 0.020 and 0.176&#xa0;s, while hard rock sites show lower averages of 0.030–0.080&#xa0;s. Vertical components generally yield smaller κ than horizontal components, consistent with global observations. The systematic partitioning analysis further confirms the strong correlation between κ values and lithological heterogeneity. By integrating site-specific κ estimations with regional geological assessments, this study provides critical insights for seismic hazard evaluation, GMPE development, and site-specific seismic design in Northeast India.</p>

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Seismic attenuation in North-East India: estimation and analysis of the kappa (κ) parameter

  • 期刊论文

  • 发表日期：

    2026年5月2日

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  • Lalramnunkimi,
  • Shikha Sharma,
  • Lalruatpuia Tlau,
  • Zosangliana Ralte,
  • Saitluanga Sailo,
  • Utsav Mannu

摘要

The seismic attenuation parameter, kappa (κ), is a critical factor in characterizing high-frequency ground motion and plays a vital role in seismic hazard assessment, ground motion prediction equation (GMPE) calibration, and site response modeling. This study investigates the spatial variability of κ in Northeast India, a tectonically active region at the convergence of the Himalayan orogeny and the Indo-Burmese arc, and examines the influence of geological and site conditions using 199 three-component seismic records from 115 earthquakes (Mw 2.5–6.8) at epicentral distances up to 400 km. κ was estimated using strong motion data from PESMOS and local broadband recordings from Mizoram, applying a modified Anderson and Hough (Bull Seismol Soc Am 74(5):1969-1993, 1984) approach with exponential decay fitting to the raw amplitude spectra. The analysis shows κ values ranging from 0.019—0.156 s for the EW component, 0.013—0.134 s for the NS component, and 0.005—0.120 s for the vertical component, with higher attenuation at sites underlain by unconsolidated sediments and alluvium with average κ values between 0.020 and 0.176 s, while hard rock sites show lower averages of 0.030–0.080 s. Vertical components generally yield smaller κ than horizontal components, consistent with global observations. The systematic partitioning analysis further confirms the strong correlation between κ values and lithological heterogeneity. By integrating site-specific κ estimations with regional geological assessments, this study provides critical insights for seismic hazard evaluation, GMPE development, and site-specific seismic design in Northeast India.