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Understanding the Variation of Seismicity in the Eastern Himalayas: Using Earthquake Frequency-Magnitude Distribution and Fractal Dimension
  • Saurav Kumar,
  • Aniruddha Sengupta
Saurav Kumar
Indian Institute of Technology Kharagpur

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Aniruddha Sengupta
Indian Institute of Technology Kharagpur
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Abstract

The Eastern 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 Mw=8.0. The 2011 (Mw= 6.9) Sikkim and 2015 (Mw= 7.8) Gorkha Nepal earthquakes call attention to the need for a more accurate understanding of seismic characteristics in the Eastern Himalayan region. In the present study, analysis of spatial variation of seismic activity in the Eastern Himalayas and its surroundings is done by analyzing the variation of seismic parameters and fractal dimension (Dc). Considering the seismicity data and tectonic features, the eastern part of the Himalayas is divided into eight seismic source zones. For the comparison of the seismicity between each seismic source zone, seismic parameters like average seismic activity rate at threshold magnitude (λo), maximum possible earthquake magnitude (Mmax), and ‘b-value’ are calculated. Seismic parameters of seismic zones are calculated by considering the incompleteness of earthquake catalogue, for that sub-catalogue is prepared for each seismic zone, which is complete to the different threshold of magnitude. The seismotectonic stress variations in Eastern 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:Eastern Himalayas; Seismicity; Fractal dimension; Seismic source zone