Stress Field and Seismicity in the Indian Shield: Effects of the Collision between India and Eurasia

1996 ◽  
pp. 503-531 ◽  
Author(s):  
T. N. Gowd ◽  
S. V. Srirama Rao ◽  
K. B. Chary
Keyword(s):  
Stress Field ◽  
Indian Shield

Stress field and seismicity in the Indian shield: Effects of the collision between India and Eurasia

1996 ◽  
Vol 146 (3-4) ◽  
pp. 503-531 ◽  
Author(s):  
T. N. Gowd ◽  
S. V. Srirama Rao ◽  
K. B. Chary
Keyword(s):  
Stress Field ◽  
Indian Shield

scholarly journals Crustal Configuration and Seismic Stability of the Eastern Indian Shield and Adjoining Regions: Insights for Incidents of Great Earthquakes in the Nepal-Bihar-Sikkim Himalaya

2021 ◽  
Vol 9 ◽  
Author(s):  
Rashmi Singh ◽  
Prosanta Kumar Khan
Keyword(s):  
Stress Field ◽  
Seismic Stability ◽  
Moho Depth ◽  
Sediment Thickness ◽  
Indian Shield ◽  
Sikkim Himalaya ◽  
Isostatic Anomaly ◽  
Fault Systems ◽  
Great Earthquakes ◽  
The Himalaya

The Eastern Indian Shield (EIS) is comprised of the intracratonic (coal-bearing) Damodar Gondwana basin, rift-controlled extensional Lower Gangetic basin (LGB), and the downward flexed Indo-Gangetic basin (IGB). The present study involves the computations and mapping of the basement configuration, sediment thickness, Moho depth, and the residual isostatic gravity anomaly, based on 2-D gravity modeling. The sediment thickness in the area ranges between 0.0 and 6.5 km, and the Conrad discontinuity occurs at ∼17.0–20 km depth. The depth of the Moho varies between 36.0 and 41.5 km, with the maximum value beneath the Upper Gangetic basin (UGB), and the minimum of ∼36 km (uplifted Moho) in the southeastern part beneath the LGB. The maximum residual isostatic anomaly of +44 mGal in the southern part indicates the Singhbhum shear zone, LGB, and Rajmahal trap to be under-compensated, whereas the northern part recording the minimum residual isostatic anomaly of –87.0 mGal is over-compensated. Although the region experienced a few moderate-magnitude earthquakes in the past, small-magnitude earthquakes are sparsely distributed. The basement reactivation was possibly associated with a few events of magnitudes more than 4.0. Toward the south, in the Bay of Bengal (BOB), seismic activities of moderate size and shallow origin are confined between the aseismic 85 and 90°E ridges. The regions on the extreme north and south [along the Himalaya and the equatorial Indian Ocean (EIO)] are experienced moderate-to-great earthquakes over different times in the historical past, but the intervening EIS and the BOB have seismic stability. We propose that the two aseismic ridges are guiding the lithospheric stress fields, which are being further focused by the basement of the EIS, the BOB, and the N-S extended regional fault systems into the bending zone of the penetrating Indian lithosphere beneath the Himalaya. The minimum obliquity of the Indian plate and the transecting fault systems in the Foothills of the Himalaya channelize and enhance the stress field into the bending zone. The enhanced stress generates great earthquakes in the Nepal-Bihar-Sikkim Himalaya, and on being reflected back through the apparently stable EIS and BOB, the stress field creates deformation and great earthquakes in the EIO.

Observation of secondary slip systems in tungsten bicrystals

1984 ◽  
Vol 42 ◽  
pp. 478-479
Author(s):  
J. R. Fekete ◽  
R. Gibala
Keyword(s):  
Stress Field ◽  
Grain Boundaries ◽  
Deformation Behavior ◽  
Stress Axis ◽  
Polycrystalline Materials ◽  
Slip Systems ◽  
Metallic Materials ◽  
Twist Boundary ◽  
Secondary Slip ◽  
Plane Normal

The deformation behavior of metallic materials is modified by the presence of grain boundaries. When polycrystalline materials are deformed, additional stresses over and above those externally imposed on the material are induced. These stresses result from the constraint of the grain boundaries on the deformation of incompatible grains. This incompatibility can be elastic or plastic in nature. One of the mechanisms by which these stresses can be relieved is the activation of secondary slip systems. Secondary slip systems have been shown to relieve elastic and plastic compatibility stresses. The deformation of tungsten bicrystals is interesting, due to the elastic isotropy of the material, which implies that the entire compatibility stress field will exist due to plastic incompatibility. The work described here shows TEM observations of the activation of secondary slip in tungsten bicrystals with a [110] twist boundary oriented with the plane normal parallel to the stress axis.

Sign in / Sign up

Export Citation Format

Share Document