- G. Surya Prakasa Rao
- V. K. Rao
- K. L. Kaila
- D. M. Mall
- B. Rajendra Prasad
- V. Vijaya Rao
- P. R. Reddy
- M. M. Dixit
- N. Madhava Rao
- V. Divakar Rao
- B. L. Narayana
- N. Madhav Rao
- A. S. N. Murty
- B. Rajendraprasad
- N. Venkateswarlu
- V. Vuaya Rao
- D. C. Mishra
- S. B. Gupta
- Prakash Kumar
- K. Sain
- Subrata K. Bhukta
- A. R. Sridhar
- N. Satyavani
- N. K. Thakur
- V. Vijay Rao
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z All
Tewari, H. C.
- Velocity Structure in Parts of the Gondwana Godavari Graben
Authors
1 National Geophysical Research Institute, Hyderabad, 500 007, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 56, No 4 (2000), Pagination: 373-384Abstract
Godavari graben, a palaeorift on the east coast of India, has been studied to delineate sedimentary thickness and basement configuration. First arrival seismic refraction data in the Chintalapudi sub-basin of Godavari graben have been utilized for 2-D ray trace modeling. Results indicate a thee layer velocity model, with velocities of 2.3-2.4, 3.2, and 4.0 kms-1 for the Gondwana (Permian to Cretaceous) sediments. Maximum depth to the basement, of velocity 55-57 kms-1, is to about 3 km in the deepest part of the sub-basin. The basement is possibly the Eastern Ghats suite of rocks. These results are in conformity with the thickness of stratigraphic sequences in a deep bore well in the basin, Another layer of velocity 5.8-6.3 kms-1 is present at about 4 km depth through out the study region, representing the base of Eastern Ghats Suite of rocks.Keywords
Godavari Graben, Gondwana, Chintalapudi Sub-Basin, Precambrian Basement, Seismic Refraction, Seismic Velocity.
- Crustal Structure and Delineation of Gondwana Basin in the Mahanadi Delta Area, India from Deep Seismic Soundings
Authors
1 National Geophysical Research Institute, Hyderabad 500007, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 29, No 3 (1987), Pagination: 293-308Abstract
A Gondwana graben with a maximum sedimentary thickness of about 2.8 km has been mapped in the Cuttack-Kendrapara area of the Mahanadi basin. This graben is bounded by faults towards its north and south. The velocities which are about 3.9 km/sec around Cuttack change to 3.4 to 3.2 km/sec towards Kendrapara. South of the Gondwana graben lies the shallow basement area, the shallowest part of which is at a depth of about 200 metres under alluvium (velocity 1.6 to 2.0 km/sec). This basement high probably formed the barrier northwest of which the Gondwana graben was formed. Southeast of this, in the coastal area and in the adjacent offshore region, new basins developed during Tertiary period which received Tertiary and younger sediments. Two coastal depressions which may be extending into the Bay of Bengal have been identified: the Konarak depression which received a maximum sedimentary thickness of about 2400 metres on land and the Paradip depression which has a maximum sedimentary thickness of 2200 metres on land. These depressions are fault-controlled and the velocity over the major part is 2.4 km/sec followed by a deeper layer with velocity 4.2 km/sec in the Konarak depression which may be represented by limestone formations or basalt flows.
In the crustal depth sections, there are velocity discontinuities at average depths of 6.0, 17.5, 20.5 and 34.5 km along various profiles which have been mapped fairly weIl. The crustal velocity model in the Mahanadi delta area shows a velocity of 1.6 km/sec at the top which is followed by a velocity of 2.45 km/sec at about 0.3 km depth. The velocity in the basement is 5.9 km/sec at a depth of 1.1 km which changes to 6.45 km/sec at 6.0 km depth. A low velocity layer about 3.0 km thick with velocity 6.0 km/ sec is indicated at 17.5 km, velocity changing to 7.1 km/sec at 20.5 km depth. The velocity at the Moho depth 34.5 km, changes to 8.1 km/sec. The crustal thickness in this area is found to be 30-34 km which is smaller than that in the Indian shield (40 km) and in the Narmada-Son lineament area (37-42 km).
- Crustal Velocity Model in the Eastern Part of the Indian Peninsular Shield
Authors
1 National Geophysical Research Institute, Hyderabad 500057, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 36, No 5 (1990), Pagination: 475-483Abstract
The velocity analysis of the first arrival refraction data, along the two deep seismic sounding profiles in the eastern part of the Indian Peninsular shield has yielded a zone of high velocity at 3 to 15km depth within the limits of the Eastern Ghat Mobile Belt towards east of the Cuddapah basin. The analysis also indicates that the crustmantle boundary in the eastern part of the Indian shield is highly disturbed due to the intrusion from the upper mantle through the lower crust and, therefore, can be termed as transitional.Keywords
Geophysics, Seismology, Eastern Ghat Mobile Belt, Cuddapah Basin, Crustal Velocity Model.- Geoscientific Studies of the Son-Narmada-Tapti Lineament Zone: Project Crumansonata
Authors
1 National Geophysical Research Institute, Hyderabad-500 007, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 48, No 1 (1996), Pagination: 112-112Abstract
No Abstract.Full Text
- Crustal Reflectivity Parameter for Deciphering the Evolutionary Processes Across the Proterozoic Aravalli-Delhi Fold Belt
Authors
1 National Geophysical Research Institute, Uppal Road, Hyderabad - 500 007, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 50, No 6 (1997), Pagination: 779-785Abstract
Deep Continental Reflection Studies along the Nagaur-Jhalawar profile across the Aravalli-Delhi Fold Belt indicate that in most of the units comprising the seismic profile the lower crust (LC) lies towards west of their present surface exposures. Based on the reflectivity characteristics of the LC. which are in general agreement with the globally accepted norms, the Nagaur-Jhalawal profile can be broadly divided into five zones: 1) the moderately reflective Marwar Basin (MB), 2) the highly reflective Delhi Fold Belt (DFB), 3) the poorly reflective Bhilwara Granite Complex (BGC), 4) the highly reflective Hindoli Group (HG) including a thrust zone, and 5) the moderately reflective Vindhyan Basin (VB). The most commonly accepted reasons for high lower crustal reflectively are: 1) presence of free fluids. 2) crustal-scale ductile shear zones and 3) mafic intrusions and underplating with partial melts derived from the upper mantle.
High reflectivity of LC in the ADFB can possibly be assigned to primary lithologic variation in the metamorphic facies layers and Precambrian shear zones that were formed during compressional phase of orogeny. The poor reflectivity of LC in the BGC. comprising the Sandmata and Mangalwar Complexes, may be due to vertically oriented igneous intrusions which have disturbed its lamellar character. The high reflectivity in the thrust zone and LC in the HG suggests that it is due to a totally different composition than that of BGC and may be related to metamorphic layering.
Keywords
Geophysics, Deep Reflection Profiling, Aravalli-Delhi Fold Belt, Seismic Profile, Rajasthan.- Nagaur-Jhalawar Geotransect Across the Delhi/Aravalli Fold Belt in Northwest India
Authors
1 National Geophysical Research Institute, Hyderabad-500007, IN
2 National Geophysical Research Institute, Hyderabad-500007
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 52, No 2 (1998), Pagination: 153-161Abstract
Lithological, gravity, magnetic, and seismic data within 100 Km corridor of the 400 km long seismic reflection profile are compiled to constitute the NW-SE Nagaur-Jhalawar Geotransect. The transect sequentially cuts across the Neo-Proterozoic Marwar Basin (MB) on the northwest, the Palaeo/Mesoproterozoic Delhi Fold Belt (DFB), the middle/late Archaean Bhilwara Gneissic Complex (BGC) and the MesolNeoproterozoic to early Palaeozoic Vindhyan Basin (VB) at the southeast. The BGC and DFB belts show polyphase deformation and metamorphism.
The BGC within the transect, consists of Sandmata Granulite Complex, followed by amphibolite facies Mangalwar Complex and Greenschist facies Hindoli/Sawar groups. The BGC show evidence of crustal reworking at c.3.0 Ga. The DFB is represented by amphibolite facies metavolcanic-metasedimentary shallow marine sequences and is tectonically highly disturbed. The DFB deposits (c. 2.0 - 1.5 Ga.) were subjected to tectonic deformation during Delhi orogeny (c. 1.5 Ga.), which is marked by syntectonic granitic plutonism. Both, the BGC and OFB also appear to have been affected by Neoproterozoic thermal events and granitic plutonism. The Neoproterozoic MB consists of clayevaporite sequences of shallow oscillatory basin deposits.
Seismic, gravitylmagnetic and magneto-telluric techniques could delineate a number of shallow to deep faults, intrusive bodies and a high conductivity zone. The total magnetic intensity shows a regional increase towards southeast. The Bouguer anomaly values show a steep rise of upto 80 mGal towards the boundary of OFB and BGC. Based on the seismic studies, doubling of the crust under the OFB and vertical intrusion of high density material under the BGC are inferred. The upper crust is, in general, transparent in its reflectivity while the lower crustal reflectivity is high in the transect area, except in the BGC and the VB. A thrust boundary, dipping NW, is present at the eastern margin of the BGC and could be traced up to 30 km depth. The Moho is at a depth of 36-38 km under the MB. Multiple Moho reflections are identified in the DFB crust, the deepest being at 45-50 km depth. In some part of the BGC the Moho can not be identified but in parts it is traced at about 50 km depth, with southeast up dip, before becoming subhorizontal at depth of 41-42 km. It becomes shallower to about 30 km depth at the SE end under the VB.
Keywords
Delhil Aravalli Fold Belt, Geotransect, Northwest India.- Velocity-Depth Relationship in Selected Parts of Indian Crust
Authors
1 National Geophysical Research Institute, Hyderabad - 500 007, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 54, No 2 (1999), Pagination: 129-136Abstract
Deep Seismic Sounding (DSS) studies were started in India in 1972, but till date no attempt has been made to synthesize the data to provide a bird's eye view of the variation in crustal model. Present synthesis of seismic data provides a glimpse of change in the regional velocity scenario as well as basement and Moho depth configurations in selected parts of the Indian crust. In the sedimentary basins of east-coast, Bengal and Cambay, the basement depth varies between 2 and 10 km, and the Proterozoic Vindhyan and Cuddapah basins show maximum depths of 5 and 10 km respectively. The maximum Moho depth is indicated as 42-44 km in the central Indian region.Keywords
Geophysics, Deep Seismic Sounding (DSS), Basement, Moho, Crustal Model.- Crustal Seismic Structure in Jammu and Kashmir Region, India
Authors
1 National Geophysical Research Institute, Uppal Road, Hyderabad - 500 007, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 69, No 4 (2007), Pagination: 755-764Abstract
A seismic line was recorded in the Jammu-Kashmir region, during the year 1978, as part of the International Pamir-Himalayan project. The data available on this line are in analog form. The first arrival refraction data in most cases appears to be reliable but only a few later arrival reflection events can be identified from four shot points. The recording is in two segments, Naoshera-Thannamandi in the Jammu region and Babarishi-Muquam in the Kashmir region. First results on the studies along this profile were published by Kaila et al. (1984). In the present interpretation, the first arrival data from the above segments were used to delineate the sedimentary basin configuration and the wide angle data to prepare a crustal model. The data were analyzed by ray inversion technique. The depth section on the Naoshera - Thannamandi segment shows a four-layered sedimentary layer configuration with velocities of 1.9, 4.1, 4.4-5.3 and 5.9-6.1 kms-l, the deepest layer being at about 4.7 km depth between Naoshera and the Main Boundary Thrust (MBT). To the north of the MBT the deepest layer is at a depth of -2.0 km. The 5.9-6.1 kms-l velocity does not seem to represent the basement of the sedimentary column, which according to hydrocarbon related geophysical and drilling results is expected at a depth exceeding 8 km in the Jammu region. The Babarishi-Maquam section shows a three-layered structure with velocities of 1.7-2.1,4.0 and 5.5-6.0 kms-l. The 5.5-6.0 kms-lvelocity is likely to represent the Panjal Traps, which form the basement for the sedimentary cover. A patchy reflection at 6.0 tolO.0 km depth in the Jarnmu region and -8.0-10.5 km depth in the Kashmir region may represent either the Precambrian or exhumed lower crustal rocks as basement, The crustal velocity model shows a layer of velocity 6.8 kms-l at -36.0 km depth and Moho with an inferred boundary velocity of 8.2 kms-l, at 40.0 - 43.0 km depth in the central part of the profile. The gravity model indicates that the Moho is deepening from -38 km at Naoshera to -48 km at Muquarn.Keywords
Seismic, Ray Tracing, Inversion, Crust, Velocity Model, Jammu & Kashmir.- Crustal Velocity Structure of the Narmada-Son Lineament along the Thuadara-Sendhwa-Sindad Profile in the NW Part of Central India and its Geodynarnic Implications
Authors
1 National Geophysical Research Institute, Uppal Road, Hyderabad - 500 007, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 69, No 6 (2007), Pagination: 1147-1160Abstract
A five-layered crustal model with 5.9-6.2, 6.0, 6.3, 6.6 and 7.0 kms-1velocities is derived with seismic refraction/wide-angle reflection data along the Thuadara-Sendhwa-Sindad profile in central India. The profile traverses across the western part of the Narmada-Son lineament in the N-S direction. The data are subjected to 2-D forward modelling using both travel times and amplitudes. Refracted waves (Pn from the Moho observed as first arrivals at a distance of about 200 km are used to derive the upper mantle velocity of 8.1 kms-'. The Moho is well constrained both from the Pn and wide-angle reflections from four shot points. The main features of the velocity structure is the delineation of a low velocity layer (6.0 kms-1) in the upper crust and a 12-16 km thick high velocity (7.0 kms-1) layer at the base of the crust. The high velocity lower crustal layer, representing the magmatic underplating in the region, may be related to the formation of the Narmada Basin and the Deccan volcanic episode. The Deccan volcanism may be a consequence of the Reunion mantle plume activity. The crustal thickness varies between 37 and 43 km along the profile and the thickest crust is found between the Narmada and Tapti rivers. The gravity mode1 constrained from the seismic velocity structure corroborates the crustal structure. Deep-seated faults responsible for the evolution of Narmada Basin are inferred from the present study.Keywords
Underplating, Deccan volcanism, Wide-Angle reflection, Low velocity layers, Moho, Narmada-Son lineament, Central India.- Upper Crustal Features as Seen from near Vertical and Wide Angle Reflections along Thuadhara-Sindad DSS Profile in Central India
Authors
1 National Geophysical Research Institute, Hyderabad, 500 007, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 63, No 2 (2004), Pagination: 204-216Abstract
Trace normalized record sections of single fold seismic data, in Central India showed several reflections of large amplitude at upper crustal depth. Synthetic seismogram modeling of these reflections, reveal that they have originated from a combination of several alternating high-tow velocity layers. On a comparison of this model with other models available worldwide, it is felt that while some of these layers may be associated with the presence of fluids, the majority should be due to lateral variations in the near surface structures. However, the first arrival refraction and wide-angle reflection data do not show a similar structure even though, a prominent upper crustal low velocity laycr could be identified.Keywords
Refraction Seismology, upper Crust, Near Vertical Reflection, Wide Angle Reflection, Low Velocity Layer, Central India.- Krishan Lai Kaila (1932-2003)
Authors
1 National Geophysical Research Institute Hyderabad - 500 007, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 62, No 3 (2003), Pagination: 391-391Abstract
No Abstract.Full Text
- Uplifted Crust in Parts of Western India
Authors
1 National Geophysical Research Institute, Hyderabad - 500 007, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 73, No 4 (2009), Pagination: 479-488Abstract
During northward movement of the Indian sub-continent, after its breakup from the Gondwanaland in the Late Cretaceous, the western part of India traversed over the Reunion plume. The Saurashtra peninsula and the Cambay Basin are two important geological regions in this part. Two and half dimensional density models, based on the crustal seismic structure, were generated to establish a relationship between these two regions. These models indicate that the crust is 32-33 km thick in the eastern Saurashtra and the northern part of the Cambay Basin. The shallower crust is in a triangular region formed by the extension of the western limb of the Proterozoic Aravalli trend in Saurashtra, its eastern limb and the Narmada fault in the south. Compared to 36-37 km thick crust to the west and 38-40 km to the east of this region the crust in the above triangular region is uplifted by 4 to 6 km. This uplift took place either after the deposition of Mesozoic sediments or was concomitant with the rise of Reunion plume prior to the extrusion of the Deccan volcanics as the region was close to the axis of the plume.Keywords
Reunion Plume, Deep Seismic, Density, Crust, Uplift, Deccan Volcanics.References
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