Analyzing The Seismic Behavior of Central Himalayan Region Using Frequency Magnitude Distribution and Fractal Dimension

The Himalayan region is a seismically active belt of arc length 2400 km extends spatially from Indus river valley (western region) to Brahmaputra river valley (eastern region) India. The Central Himalayan region, along with its neighboring area is known to be the part of the `Alpine-Himalayan global seismic belt', a seismically active area of the world. In the past (1897, 1905, 1934, and 1950) four great earthquakes have triggered in this region with a magnitude higher than M =8.0. The 2015 (M = 7.8) Gorkha Nepal earthquakes call attention to the need for a more accurate understanding of seismic characteristics in the Central Himalayan region. In the present study, analysis of spatial variation of seismic activity in the Central Himalayas covering the Indian state of Himachal Pradesh, Uttarakhand and Western part of Nepal is done by analyzing the variation of seismic parameters and fractal dimension (Dc) using the updated and homogeneous earthquake catalogue of the study area. Considering the earthquake distribution and tectonic features, the central Himalayas is divided into 12 seismic source zones. For the comparison of the seismicity between each seismic source zone, seismic parameters such as seismic activity rate (λ), maximum possible earthquake magnitude (Mmax), and `b-value' are calculated. The b value varies from 0.7 to 1.05 in the study area and clustering of seismic event is prominent in western part of Nepal The seismotectonic stress variations in Central Himalayas are indicated by the estimated values of b and Dc. The calculated seismic parameters can be used directly for seismic hazard analysis of the study area.

Keywords: Seismicity; Himalayas; Fractal Dimension; Frequency Magnitude Distribution