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Abstract <p>This research examines the seismicity features of the Alborz region based on a clustered earthquake catalog from the Hierarchical Density-Based Spatial Clustering of Applications with Noise (HDBSCAN) algorithm. The frequency magnitude distribution (FMD), which is derived from the Gutenberg–Richter relation, indicates a completeness magnitude (Mc) of 2.6, thereby validating the catalog. The calculated b-value of 0.68 ± 0.01 is lower than the global mean, showing high differential stress and an increased likelihood for large earthquakes, while the a-value of 5.057 (annual equivalent 3.782) shows a high rate of regional seismicity. Spatial b-value, fractal parameter (Dc-value), and LogM<sub>0</sub> variation emphasize large-scale tectonic heterogeneity: low b-values along master faults (e.g., North Alborz, Khazar, Mosha) are linked to asperity growth and focal stress concentration, whereas high b-values in surrounding areas indicate ductile deformation and repeated low-magnitude seismic activity. Seismic quiescence (Z-value) determinations across various temporal windows also emphasize an east–west hazard gradient with a higher-stress buildup and higher seismic potential in the eastern Alborz. These findings depict the Alborz as a highly seismically active area and highlight the importance of incorporating spatially variable seismic parameters into probabilistic hazard analysis and risk mitigation schemes in this urbanized region.</p> Highlights <p>• The Alborz region shows a low b-value (0.68 ± 0.01) and high a-value, reflecting strong differential stress, elevated seismicity rates, and high potential for large earthquakes.</p> <p>• Low b-values and high Dc-values along major faults (North Alborz, Khazar, Mosha) reveal asperity growth, fault locking, and brittle rupture processes, while surrounding areas exhibit ductile deformation and repeated small events.</p> <p>• Z-value analysis highlights an east–west asymmetry, with the eastern Alborz experiencing greater stress buildup, higher strain accumulation, and increased seismic hazard compared to the western sector.</p>

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Comprehensive spatio-temporal analysis of seismicity parameters in the Alborz Region using the HDBSCAN algorithm

  • 期刊论文

  • 发表日期：

    2026年3月3日

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  • Muhammed Hossein Mousavi,
  • Faegheh Mina Araghi,
  • Parva Sadeghi Alavijeh

摘要

Abstract

This research examines the seismicity features of the Alborz region based on a clustered earthquake catalog from the Hierarchical Density-Based Spatial Clustering of Applications with Noise (HDBSCAN) algorithm. The frequency magnitude distribution (FMD), which is derived from the Gutenberg–Richter relation, indicates a completeness magnitude (Mc) of 2.6, thereby validating the catalog. The calculated b-value of 0.68 ± 0.01 is lower than the global mean, showing high differential stress and an increased likelihood for large earthquakes, while the a-value of 5.057 (annual equivalent 3.782) shows a high rate of regional seismicity. Spatial b-value, fractal parameter (Dc-value), and LogM0 variation emphasize large-scale tectonic heterogeneity: low b-values along master faults (e.g., North Alborz, Khazar, Mosha) are linked to asperity growth and focal stress concentration, whereas high b-values in surrounding areas indicate ductile deformation and repeated low-magnitude seismic activity. Seismic quiescence (Z-value) determinations across various temporal windows also emphasize an east–west hazard gradient with a higher-stress buildup and higher seismic potential in the eastern Alborz. These findings depict the Alborz as a highly seismically active area and highlight the importance of incorporating spatially variable seismic parameters into probabilistic hazard analysis and risk mitigation schemes in this urbanized region.

Highlights

• The Alborz region shows a low b-value (0.68 ± 0.01) and high a-value, reflecting strong differential stress, elevated seismicity rates, and high potential for large earthquakes.

• Low b-values and high Dc-values along major faults (North Alborz, Khazar, Mosha) reveal asperity growth, fault locking, and brittle rupture processes, while surrounding areas exhibit ductile deformation and repeated small events.

• Z-value analysis highlights an east–west asymmetry, with the eastern Alborz experiencing greater stress buildup, higher strain accumulation, and increased seismic hazard compared to the western sector.