Crustal velocity structure of western Dharwar Craton, South India

Sarkar, Dipankar; Chandrakala, K.; Devi, P. Padmavathi; Sridhar, Alpa; Sain, Kalachand; Reddy, P. R.

doi:10.1016/s0264-3707(00)00021-1

Cited by 53 publications

(28 citation statements)

References 18 publications

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“…Crustal thickness in the Closepet Granite region, estimated from deep seismic sounding studies along a profile cutting across the Dharwar craton, from Udupi in the west to Kavali in the east (Fig. 1), has a range 35-40 km with a mean of *37 km (Kaila et al 1979;Sarkar et al 2001). Interpretation of gravity data along a NE-SW profile in the northern part of the craton reveals a variation in crustal thickness from 35 to 41 km (Mishra et al 2002).…”

Section: Crustal Heat Production Models and Mantle Heat Flow Estimatesmentioning

confidence: 99%

Heat flow and crustal thermal structure in the Late Archaean Closepet Granite batholith, south India

Roy

Ray

Bhattacharya

et al. 2007

Int J Earth Sci (Geol Rundsch)

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The Late Archaean Closepet Granite batholith in south India is exposed at different crustal levels grading from greenschist facies in the north through amphibolite and granulite facies in the south along a *400 km long segment in the Dharwar craton. Two areas, Pavagada and Magadi, located in the Main Mass of the batholith, best represent the granitoid of the greenschist and amphibolite facies crustal levels respectively. Heat flow estimates of 38 mW m -2 from Pavagada and 25 mW m -2 from Magadi have been obtained through measurements in deep (430 and 445 m) and carefully sited boreholes. Measurements made in four boreholes of opportunity in Pavagada area yield a mean heat flow of 39 ± 4 (s.d.) mW m -2 , which is in good agreement with the estimate from deep borehole. The study, therefore, demonstrates a clear-cut heat flow variation concomitant with the crustal levels exposed in the two areas. The mean heat production estimates for the greenschist facies and amphibolite facies layers constituting the Main Mass of the batholith are 2.9 and 1.8 lW m -3 , respectively. The enhanced heat flow in the Pavagada area is consistent with the occurrence of a radioelement-enriched 2-km-thick greenschist facies layer granitoid overlying the granitoid of the amphibolite facies layer which is twice as thick as represented in the Magadi area. The crustal heat production models indicate similar mantle heat flow estimates in the range 12-14 mW m -2 , consistent with the other parts of the greenstone-granite-gneiss terrain of the Dharwar craton.

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Section: Crustal Heat Production Models and Mantle Heat Flow Estimatesmentioning

confidence: 99%

Heat flow and crustal thermal structure in the Late Archaean Closepet Granite batholith, south India

Roy

Ray

Bhattacharya

et al. 2007

Int J Earth Sci (Geol Rundsch)

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“…Here, the shear wave velocity (V S ) in the source region is taken as 4.2 km/s (Sarkar et al, 2001). The diminution function D(f ) is defined as…”

Section: Synthetic Earthquake Data Generationmentioning

confidence: 99%

Seismic Hazard Analysis for the Bangalore Region

Sitharam

Anbazhagan

2006

Nat Hazards

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Indian peninsular shield, which was once considered to be seismically stable, is experiencing many earthquakes recently. As part of the national level microzonation programme, Department of Science and Technology, Govt. of India has initiated microzonation of greater Bangalore region. The seismic hazard analysis of Bangalore region is carried out as part of this project. The paper presents the determination of maximum credible earthquake (MCE) and generation of synthetic acceleration time history plot for the Bangalore region. MCE has been determined by considering the regional seismotectonic activity in about 350 km radius around Bangalore city. The seismotectonic map has been prepared by considering the faults, lineaments, shear zones in the area and historic earthquake events of more than 150 events. Shortest distance from the Bangalore to the different sources is measured and then peak ground acceleration (PGA) is calculated for the different source and moment magnitude. Maximum credible earthquake found in terms of moment magnitude is 5.1 with PGA value of 0.146 g at city centre with assuming the hypo central distance of 15.88 km from the focal point. Also, correlations for the fault length with historic earthquake in terms of moment magnitude, yields (taking the rupture fault length as 5% of the total fault length) a PGA value of 0.159 g. Acceleration time history (ground motion) and a response acceleration spectrum for the corresponding magnitude has been generated using synthetic earthquake model considering the regional seismotectonic parameters. The maximum spectral acceleration obtained is 0.332 g for predominant period of 0.06 s. The PGA value and synthetic earthquake ground motion data from the identified vulnerable source using seismotectonic map will be useful for the PGA mapping and microzonation of the area.

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“…Moreover, the petrological and seismological evidence indicates that the lower crustal densities probably do not exceed about 3,060 kg m -3 (MENKE, 1999). The Pn velocity, a major source of information on the petrologic nature of the upper mantle, varies from 8.59 km s -1 beneath the western Dharwar craton to 7.8 km s -1 beneath the eastern Dharwar craton with 8.0 km s -1 beneath the SGT (KAILA et al, 1979, REDDY et al, 2000, 2003SARKAR et al, 2001). The three-dimensional P-wave velocity tomography using teleseismic rays from a variety of azimuths also indicates 2-3% lower velocities at the depth range of 40-177 km beneath the SGT compared to the Dharwar craton (SRINAGESH and RAI, 1996).…”

Section: Possible Evidence Of Density Contrast Reductionmentioning

confidence: 99%

Insights into the Crustal Structure and Geodynamic Evolution of the Southern Granulite Terrain, India, from Isostatic Considerations

Kumar

Singh

2010

Pure Appl. Geophys.

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The Southern Granulite Terrain of India, formed through an ancient continental collision and uplift of the earth's surface, was accompanied by thickening of the crust. Once the active tectonism ceased, the buoyancy of these deep crustal roots must have supported the Nilgiri and Palani-Cardamom hills. Here, the gravity field has been utilized to provide new constraints on how the force of buoyancy maintains the state of isostasy in the Southern Granulite Terrain. Isostatic calculations show that the seismically derived crustal thickness of 43-44 km in the Southern Granulite Terrain is on average 7-8 km more than that required to isostatically balance the present-day topography. This difference cannot be solely explained applying a constant shift in the mean sea level crustal thickness of 32 km. The isostatic analysis thus indicates that the current topography of the Southern Granulite Terrain is overcompensated, and about 1.0 km of the topographic load must have been eroded from this region without any isostatic readjustment. The observed gravity anomaly, an order of magnitude lower than that expected (-125 mGal), however, shows that there is no such overcompensation. Thermal perturbations up to Pan-African, present-day high mantle heat flow and low Te together negate the possible resistance of the lithosphere to rebound in response to erosional unloading. To isostatically compensate the crustal root, compatible to seismic Moho, a band of high density (2,930 kg m -3 ) in the lower crust and low density (3,210 kg m -3 ) in the lithospheric mantle below the Southern Granulite Terrain is needed. A relatively denser crust due to two distinct episodes of metamorphic phase transitions at 2.5 Ga and 550 Ma and highly mobilized upper mantle during Pan-African thermal perturbation reduced significantly the root buoyancy that kept the crust pulled downward in response to the eroded topography.

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Crustal velocity structure of western Dharwar Craton, South India

Cited by 53 publications

References 18 publications

Heat flow and crustal thermal structure in the Late Archaean Closepet Granite batholith, south India

Heat flow and crustal thermal structure in the Late Archaean Closepet Granite batholith, south India

Seismic Hazard Analysis for the Bangalore Region

Insights into the Crustal Structure and Geodynamic Evolution of the Southern Granulite Terrain, India, from Isostatic Considerations

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