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Chander, R.
- On the Active Tectonics of Dehra Dun Region from Observations of Ground Elevation Changes
Authors
1 Department of Earth Sciences, University of Roorkee, Roorkee 247667, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 39, No 1 (1992), Pagination: 61-68Abstract
The data presented suggest that uplift of the outer Himllaya in this region is continuing even today through sudden co-seismic elevation changes during large thrust earthquakes and secular aseismic uplift during intervals between such earthquakes. The observed co-seismic ground elevation changes during the Kangra earthquake are interpreted so as to simulate the cross-sectional shape of the buried active thrust fault responsible for this continuing episodie as well as secular uplift of the Outer Himalaya. This fault is assumed to be the surface of detachment between the Himalayan rocks above and the Indian shield rocks below. It is concluded that over most of its extent in Dehra Dun region, the detachment surface has gentle dip to the northeast but a few interspersed, northeast dipping steeper ramps are not ruled out. The depth of the detachment is estimated to be between 0 and 3 km beneath the SW limit and about 10 km beneath the NE limit of the Outer Himalaya in the Dehra Dun region. The two main levelling observations regarding the current inactive status of the Main Boundary Thrust (MBT) are, (1) the involvement of this thrust in the occurrence of the Kangra earthquake is definitely ruled out from the levelling data, and (2) the measured rate of secular uplift of the ground increases from NE to SW across the surface trace of the thrust suggesting that the Outer Himalaya is rising faster than the Lesser Himalaya to the NE across the MBT.Keywords
Ground Elevation, Earthquake, Tectonism, Dehra Dun.- Remote Sensing Delineation of Zones Susceptible to Seismically Induced Liquefaction in the Ganga Plains
Authors
1 Department of Earth Sciences. University of Roorkee, Roorkee-247667, IN
2 Department of Earth Sciences, University of Roorkee, Roorkee-247667, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 46, No 1 (1995), Pagination: 75-82Abstract
Liquefaction in saturated sandy soils as a result of earthquake-induced shaking, poses a major threat to men and materials. Many parts of the Indo-Gangetic plains have experienced such catastrophes repeatedly. The border region of southern Nepal-northern Bihar (India) is a typical existing setting prone to soil liquefaction in the Indo-Gangetic Plains. The Bihar-Nepal earthquake of 1934 (Ms>8) and the earthquake of 1988 (Mb = 6.7) induced extensive liquefaction in the terrain in living memory. Characteristics of soil in this area of nothern Bihar have been determined from field samples. Various parameters (e.g. clay content, D50 - and C-values) indicate high susceptibility to liquefaction among soils in the area.
A close study of remote sensing data (Landsat TM and MSS) products reveals that the boundaries of liquefaction zone in the Bihar-Nepal region during the 1934 earthquake are identifiable on the remote sensing images. This is due to a combination of several inter-related factors, such as landform, soil type, soil moisture and vegetation. These clues have been applied as guides on the adjoining remote sensing images for delineating areas on a regional scale, where liquefaction might possibly occur in the Ganga plains, in the event of future Himalayan earthquakes.
Keywords
Earthquakes, Ganga Plains, Remote Sensing, Seismology.- Evidence from Earthquake Fault Plane Solutions on Upper Crustal Stresses in the Garhwahl Himalaya
Authors
1 Department of Earth sciences, University of Roorkee, Roorkee-247 667, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 45, No 6 (1995), Pagination: 695-701Abstract
The individual thrust-fault type fault plane solution of the 1991 Uttarkashi earthquake is considered along with a reverse fault type and a strike-slip type composite fault plane solutions for the Garhwal Himalaya. The two latter solutions are based on data from 49 small and micro-earthquakes. All 50 earthquakes occured in the vicinityof Main Central Thrust over a distance of about 150km from Yamuna to Alaknanda valleys. The data are consistent with the view that a thrust-fault type stress environment prevails throughout the uppercrust in the region. The maximum effective principal stress (σ1) is horizontal to sub-horizontal with azimuth along N42° everywhere in the upper crust except in the hypocental region of the Utrarkashi earthquake, where it is N26°. lntermediate effective principal stress (σ2)is horizontal in the NW quadrant and the minimum effective principal stress (σ3) is vertical to sub-vertical correspondingly. Reactivation of the strike-slip faults occurs under the influence of σ1 and σ2. This is within the theory of fault reactivation under general three dimensional stresses. Pore pressures could be relatively high and may approach lithostatic levels over most parts of upper crust in the region.Keywords
Seismology, Garhwal Himalaya.- Geotectonic and Seisnlic Risk Implications of Ground Level Changes in the Dehradun Region during the 1905-28 Period
Authors
1 Department of Earth Sciences, University of Roorkee, Roorkee - 247 667, IN