Recent seismicity in Northeast India and its adjoining region |
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| Authors: | Kiran Kumar Singh Thingbaijam Sankar Kumar Nath Abhimanyu Yadav Abhishek Raj M Yanger Walling William Kumar Mohanty |
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| Institution: | (1) Department of Geology and Geophysics, Indian Institute of Technology, Kharagpur, India |
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| Abstract: | Recent seismicity in the northeast India and its adjoining region exhibits different earthquake mechanisms – predominantly
thrust faulting on the eastern boundary, normal faulting in the upper Himalaya, and strike slip in the remaining areas. A
homogenized catalogue in moment magnitude, M
W, covering a period from 1906 to 2006 is derived from International Seismological Center (ISC) catalogue, and Global Centroid
Moment Tensor (GCMT) database. Owing to significant and stable earthquake recordings as seen from 1964 onwards, the seismicity
in the region is analyzed for the period with spatial distribution of magnitude of completeness m
t, b value, a value, and correlation fractal dimension D
C. The estimated value of m
t is found to vary between 4.0 and 4.8. The a value is seen to vary from 4.47 to 8.59 while b value ranges from 0.61 to 1.36. Thrust zones are seen to exhibit predominantly lower b value distribution while strike-slip and normal faulting regimes are associated with moderate to higher b value distribution. D
C is found to vary from 0.70 to 1.66. Although the correlation between spatial distribution of b value and D
C is seen predominantly negative, positive correlations can also be observed in some parts of this territory. A major observation
is the strikingly negative correlation with low b value in the eastern boundary thrust region implying a possible case of extending asperity. Incidentally, application of
box counting method on fault segments of the study region indicates comparatively higher fractal dimension, D, suggesting an inclination towards a planar geometrical coverage in the 2D spatial extent. Finally, four broad seismic source
zones are demarcated based on the estimated spatial seismicity patterns in collaboration with the underlying active fault
networks. The present work appraises the seismicity scenario in fulfillment of a basic groundwork for seismic hazard assessment
in this earthquake province of the country. |
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| Keywords: | b value a value Correlation fractal dimension Northeast India Seismicity |
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