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Background <p>The Kashmir Valley, situated within the northwest segment of the Himalayan orogen, representsa seismotectonically active intramontane basin. Its seismicity is governed by the ongoing India–Eurasia plateconvergence at ~35–45 mm/yr and the reactivation of intra-basinal fault networks, including the Magam andBalapora fault systems. These tectonic structures accommodate distributed deformation through a complexinterplay of thrust, strike-slip, and normal faulting mechanisms. Given its high population density and criticalinfrastructure, characterizing the seismic behaviour, magnitude–frequency distribution, and recurrence potential ofearthquakes in this basin is essential for advancing probabilistic seismic hazard assessment (PSHA) and reducingseismic risk in the region.</p> Methods <p>High-quality seismic data recorded by a local seismic network between 2019 and2022, with a sampling interval of one second, were analysed. A total of 488 earthquakes with local magnitudes(ML) ranging from 1.0 to 5.2 were examined. The Gutenberg-Richter parameters, including the b-value andmagnitude of completeness (Mc), were estimated. Focal Mechanism Solutions (FMS) for events with Mw ≥ 3.0were determined using first-motion polarity data. Additionally, a Poisson probability model was applied to evaluaterecurrence intervals across various magnitude ranges.</p> Results <p>The Gutenberg-Richter b-value was calculated as 0.65± 0.03, indicating a relatively high proportion of moderate to large magnitude earthquakes and elevated tectonicstress levels. The Mc value of 2.90 confirmed the robustness of the dataset for statistical analysis. FMS revealed amixture of thrust, normal, and strike-slip faulting, highlighting the active role of intra-basinal structures such as theMagam and Balapora faults in shaping regional seismicity. Probabilistic analysis suggested that smaller earthquakes(ML &lt; 4.2) are likely to occur every 0.1 years, whereas large-magnitude events (ML ≥ 7.2) may have recurrenceintervals of up to 100 years.</p> Discussion <p>The integration of seismic catalogue analysis, focal mechanism studies, andprobabilistic recurrence modelling provides a comprehensive assessment of the present tectonic regime in theKashmir Valley. The results underline the elevated seismic hazard posed by both frequent small events and thepotential for infrequent but damaging large earthquakes. These findings have significant implications for seismichazard assessment and risk mitigation, emphasizing the necessity for resilient infrastructure and proactive policymeasures in this earthquake-prone region.</p>

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Assessment of seismicity using local broadband seismic network: a case study from Kashmir valley, NW, Himalaya, India

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  • 发表日期：

    2025年9月30日

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  • Bikram Singh Bali,
  • Nayeem Ahmad Bhat,
  • Ahsan Afzal Wani,
  • Sareer Ahmad Mir,
  • Naseer Ahmad Bhat

摘要

Background

The Kashmir Valley, situated within the northwest segment of the Himalayan orogen, representsa seismotectonically active intramontane basin. Its seismicity is governed by the ongoing India–Eurasia plateconvergence at ~35–45 mm/yr and the reactivation of intra-basinal fault networks, including the Magam andBalapora fault systems. These tectonic structures accommodate distributed deformation through a complexinterplay of thrust, strike-slip, and normal faulting mechanisms. Given its high population density and criticalinfrastructure, characterizing the seismic behaviour, magnitude–frequency distribution, and recurrence potential ofearthquakes in this basin is essential for advancing probabilistic seismic hazard assessment (PSHA) and reducingseismic risk in the region.

Methods

High-quality seismic data recorded by a local seismic network between 2019 and2022, with a sampling interval of one second, were analysed. A total of 488 earthquakes with local magnitudes(ML) ranging from 1.0 to 5.2 were examined. The Gutenberg-Richter parameters, including the b-value andmagnitude of completeness (Mc), were estimated. Focal Mechanism Solutions (FMS) for events with Mw ≥ 3.0were determined using first-motion polarity data. Additionally, a Poisson probability model was applied to evaluaterecurrence intervals across various magnitude ranges.

Results

The Gutenberg-Richter b-value was calculated as 0.65± 0.03, indicating a relatively high proportion of moderate to large magnitude earthquakes and elevated tectonicstress levels. The Mc value of 2.90 confirmed the robustness of the dataset for statistical analysis. FMS revealed amixture of thrust, normal, and strike-slip faulting, highlighting the active role of intra-basinal structures such as theMagam and Balapora faults in shaping regional seismicity. Probabilistic analysis suggested that smaller earthquakes(ML < 4.2) are likely to occur every 0.1 years, whereas large-magnitude events (ML ≥ 7.2) may have recurrenceintervals of up to 100 years.

Discussion

The integration of seismic catalogue analysis, focal mechanism studies, andprobabilistic recurrence modelling provides a comprehensive assessment of the present tectonic regime in theKashmir Valley. The results underline the elevated seismic hazard posed by both frequent small events and thepotential for infrequent but damaging large earthquakes. These findings have significant implications for seismichazard assessment and risk mitigation, emphasizing the necessity for resilient infrastructure and proactive policymeasures in this earthquake-prone region.