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<p>This study presents a comprehensive seismic hazard assessment of Northeast India, one of the most seismically active regions globally due to the interaction of the Indian–Eurasian plate collision and the Burmese subduction zone. The region’s complex tectonics and history of devastating earthquakes, including the 1897 Shillong and 1950 Great Assam events, highlight the urgent need for updated hazard evaluation to support disaster risk reduction and resilient infrastructure planning. The study introduces an updated multi-regression magnitude homogenization with multiple declustering techniques, period and magnitude completeness assessment, refined source zonation and seismicity analysis integrated with established Ground Motion Prediction Equations (GMPEs) within a logic-tree framework to develop a Probabilistic Seismic Hazard Analysis (PSHA) model for the region. An extensive earthquake catalogue (1762–2022) was compiled and homogenized using four regression techniques: Standard Least-squares Regression (SLR), General Orthogonal Regression (GOR), Orthogonal Standard Regression (OSR), and Inverse Standard Regression (ISR). Mainshock events were identified through three declustering algorithms: Gruenthal, Gardner and Knopoff, and Uhrhammer. Catalogue completeness was analyzed using Stepp’s method for five delineated seismic source zones, followed by estimation of seismicity parameters. PSHA was conducted for areal source zones using regionally appropriate GMPEs, targeting engineering bedrock conditions. The results indicate Peak Ground Acceleration values of 0.19–0.44&#xa0;g and 0.43–0.83&#xa0;g for 10% and 2% probability of exceedance in 50&#xa0;years, respectively. Spectral Accelerations at 0.2&#xa0;s and 1.0&#xa0;s, along with Uniform Hazard Spectra (UHS) for all state capitals, provide robust, updated hazard estimates vital for site-specific design, urban planning, and seismic risk mitigation across Northeast India.</p>

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Seismicity patterns and seismogenic framework for Northeast India: implications for regional hazard assessment

  • 期刊论文

  • 发表日期：

    2026年5月27日

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  • Komal Soni,
  • Daya Shanker

摘要

This study presents a comprehensive seismic hazard assessment of Northeast India, one of the most seismically active regions globally due to the interaction of the Indian–Eurasian plate collision and the Burmese subduction zone. The region’s complex tectonics and history of devastating earthquakes, including the 1897 Shillong and 1950 Great Assam events, highlight the urgent need for updated hazard evaluation to support disaster risk reduction and resilient infrastructure planning. The study introduces an updated multi-regression magnitude homogenization with multiple declustering techniques, period and magnitude completeness assessment, refined source zonation and seismicity analysis integrated with established Ground Motion Prediction Equations (GMPEs) within a logic-tree framework to develop a Probabilistic Seismic Hazard Analysis (PSHA) model for the region. An extensive earthquake catalogue (1762–2022) was compiled and homogenized using four regression techniques: Standard Least-squares Regression (SLR), General Orthogonal Regression (GOR), Orthogonal Standard Regression (OSR), and Inverse Standard Regression (ISR). Mainshock events were identified through three declustering algorithms: Gruenthal, Gardner and Knopoff, and Uhrhammer. Catalogue completeness was analyzed using Stepp’s method for five delineated seismic source zones, followed by estimation of seismicity parameters. PSHA was conducted for areal source zones using regionally appropriate GMPEs, targeting engineering bedrock conditions. The results indicate Peak Ground Acceleration values of 0.19–0.44 g and 0.43–0.83 g for 10% and 2% probability of exceedance in 50 years, respectively. Spectral Accelerations at 0.2 s and 1.0 s, along with Uniform Hazard Spectra (UHS) for all state capitals, provide robust, updated hazard estimates vital for site-specific design, urban planning, and seismic risk mitigation across Northeast India.