Assessment of the earthquake hazard in the Ladakh and neighbouring Himalayan region (India) utilizing three-dimensional modelling of b-value and fractal (correlation) dimensions

Abstract Background This study investigates the seismic characteristics of Ladakh and its tectonically active surroundings through threedimensional fractal correlation dimensions and b-value analysis. Using the ISC catalogue from 1905 to 2023, we analyzed 1059 earthquakes with magnitudes between M w 4.0-7.9. Maximum likelihood estimation was employed for b-value calculation, while fractal dimensions were modeled using the correlation dimensions approach to evaluate seismic hazard zones across the region. Results The Ladakh Himalayan sequence exhibits an overall b-value of 0.77 ± 0.02, with spatial variations ranging from 0.38 to 4.11 across the study area. Correlation dimensions (D 2 ) range from 0.16 to 1.47, indicating significant spatial heterogeneity in fracture patterns. A positive correlation between b-values and D was established (D 2 = 0.652 + 0.133 b), which satisfies Aki's hypothesized relationship D = 3b/c for single fracturing events. Spatial distribution analysis identified four distinct hazard zones: (1) Zone A (intermediate hazard) - characterized by lower to moderate b-values and moderate correlation dimensions, typical of the Ladakh region; (2) Zones B and C (high hazard) - distinguished by coherent fault structures with fewer, larger faults including the Main Central Thrust, Kaurik Chango fault, and Karakoram Fault; and (3) Zone D (low hazard) - exhibiting high D 2 and moderate to high b-values, suggesting fluid-rich regions where stress is distributed across many small fractures. Conclusion The positive b-D 2 correlation in the Ladakh Himalayan region may indicate either aseismic slip, frequent occurrences of smaller earthquakes reducing the potential for large megathrust events, or distributed deformation patterns rather than localized ruptures. Our findings suggest that the Ladakh region experiences moderate tectonic stress, making it prone to mild to moderate earthquakes in the future. In contrast, the surrounding Himalayan areas exhibit considerably higher tectonic stress, indicating a greater probability of moderate to large earthquakes. This spatial variation in seismic characteristics provides valuable information for regional seismic hazard assessment and disaster management planning.