b- value mapping in Sikkim and adjoining Himalayas

The b-value in the frequency-magnitude relation is one of the fundamental seismological parameters to define an assemblage of earthquakes. This study focuses on the use of b-value as a precursor to know the chances of occurrence of major earthquake events in Sikkim and adjoining Himalayas. A catalogue containing 9192 earthquakes (M ≥ 0.30) recorded across Nepal, Sikkim and Bhutan Himalayas during 1980-2022 is considered for the present study. The study area has been divided into three blocks encompassing Nepal, Sikkim and Bhutan segments and the b-values are computed. The results show variations in b-value across these three blocks which might be associated with the differential stress pattern across the regions. Further, we map the spatial variation of frequency-magnitude distribution by dividing the entire region into 0.1⁰ x 0.1⁰ grids. The grids with less than 30 earthquake events are excluded to ensure the reliability of our results. The results suggest that the entire segment belongs to a high stressed region. The lowest b-values are mostly observed in Sikkim and western Nepal, reflecting the possible zones of future earthquakes.