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<p>This study uses the Das magnitude scale (M<sub>wg</sub>) to improve probabilistic seismic hazard assessment (PSHA) in Northeast India, where traditional M scales introduce inaccuracies for events below M 7.5. The M scale is mathematically flawed in this range, being based on an equation derived for Ms ≲ 7.0—an inconsistency evident in the observed data. Using a unified earthquake catalog of 9,968 events, calibrated to M<sub>wg</sub>, in conjunction with region-specific seismogenic zones and observed-data-validated ground motion models, hazard spectra were derived for 475- and 2475-year return periods. The resulting PSHA indicates maximum peak ground accelerations (PGA) of 0.908&#xa0;g and 1.5405&#xa0;g for 10% and 2% exceedance probabilities over 50&#xa0;years, respectively. Comparative analysis revealed significant discrepancies between M and M<sub>wg</sub>, with M overestimating ground motion by up to 40% for the 475-year return period and 20% for The 2475-year return period, particularly in regions prone to medium-range earthquakes. This overestimation of the M scale (mainly for smaller and medium earthquakes) was previously reported by Choy and Boatwright in 1995 using the Gutenberg–Richter energy equation. This issue can be effectively addressed by adopting the M<sub>wg</sub> scale, which provides a more accurate representation of seismic energy. Furthermore, M scale underestimated PGA by up to 10% for very large magnitude events. These discrepancies, particularly overestimation in smaller and medium earthquake ranges, have critical implications for structural design. The adoption of M<sub>wg</sub> provides a more accurate seismic hazard representation, necessitating a reevaluation of current building codes and emergency response protocols in Northeast India.</p>

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Updated probabilistic seismic hazard assessment using Mwg (Das magnitude scale) to address moment magnitude (M) scale inaccuracies below 7.5: a case study from Northeast India

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  • 出版模式：

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  • 发表日期：

    2025年11月27日

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  • Ranjit Das,
  • Arindam Das,
  • Deepankar Choudhury,
  • Claudio Meneses,
  • Francisco García Barrera,
  • Hans Raj Wason,
  • Mohammad Ayaz Alam

摘要

This study uses the Das magnitude scale (Mwg) to improve probabilistic seismic hazard assessment (PSHA) in Northeast India, where traditional M scales introduce inaccuracies for events below M 7.5. The M scale is mathematically flawed in this range, being based on an equation derived for Ms ≲ 7.0—an inconsistency evident in the observed data. Using a unified earthquake catalog of 9,968 events, calibrated to Mwg, in conjunction with region-specific seismogenic zones and observed-data-validated ground motion models, hazard spectra were derived for 475- and 2475-year return periods. The resulting PSHA indicates maximum peak ground accelerations (PGA) of 0.908 g and 1.5405 g for 10% and 2% exceedance probabilities over 50 years, respectively. Comparative analysis revealed significant discrepancies between M and Mwg, with M overestimating ground motion by up to 40% for the 475-year return period and 20% for The 2475-year return period, particularly in regions prone to medium-range earthquakes. This overestimation of the M scale (mainly for smaller and medium earthquakes) was previously reported by Choy and Boatwright in 1995 using the Gutenberg–Richter energy equation. This issue can be effectively addressed by adopting the Mwg scale, which provides a more accurate representation of seismic energy. Furthermore, M scale underestimated PGA by up to 10% for very large magnitude events. These discrepancies, particularly overestimation in smaller and medium earthquake ranges, have critical implications for structural design. The adoption of Mwg provides a more accurate seismic hazard representation, necessitating a reevaluation of current building codes and emergency response protocols in Northeast India.