Seismic <Emphasis Type="Italic">b</Emphasis>-Value and the Assessment of Ambient Stress in Northeast India |
| |
| Authors: | Prosanta Kumar Khan Manoj Ghosh Partha Pratim Chakraborty Debdeep Mukherjee |
| |
| Institution: | (1) Department of Applied Geophysics, Indian School of Mines, Dhanbad, 826 004, India;(2) Reliance Industries Limited, Seismic Data Acquisition and Processing Group, Mumbai, India;(3) Department of Geology, University of Delhi, New Delhi, 110007, India |
| |
| Abstract: | Seismicity data of northeast India, recorded between 1986 and 1999 by a local network, are analysed for estimation of b-values. Based on the obtained values, viz. low (b ≤ 0.5), moderate (0.5 < b ≤ 0.7) and high (b > 0.7), the study area is classified into different seismic-domains. An assessment of stress level is also carried out in
identifying seismic-domains. Seismic activities, though mostly confined in some sectors, are presumably triggered by mutual
interaction of the Shillong Plateau, Mikir Hills, Indo-Burman Ranges and the easternmost part of the Himalayas, and the contributions
from deep-seated fractures cannot be ignored. The results resemble the seismic character of a foreland setting adjacent to
a convergent margin. The b-values estimated for 240 square grids of dimension 0.6° × 0.6° over five seismic domains indicate wide variation. An analysis
of cumulative seismic moment release (M
O) in different layers also indicates an anomaly in reference to the total seismic-energy budget of the five zones. The lower
b-value and higher M
O recorded at relatively lower depth (~30 km) towards the southwest of the study area might be associated with upward bulging
of a strong lithosphere. The bulging is perhaps regionally compensated by the downward flexing of the descending Indian lithosphere
beneath the Upper Assam area; features unequivocally observed in any foreland setup. Towards the north and east of the study
area, random variations of in both b-value and M
O along the converging zone suggest a varied tectonic environment with active interaction between the tectonic elements in
these areas. |
| |
| Keywords: | |
| 本文献已被 SpringerLink 等数据库收录！ |
|
