Abstract
<p>We measure the inter-station Rayleigh and Love wave phase velocities across the northwestern Indian Peninsular shield (NW-IP) through cross-correlation and invert these velocities to evaluate the underneath crust and upper mantle velocity structure down to 400 km. We consider a cluster of three stations in the northern tip of the Peninsula and another cluster of eight stations in the south. We measure phase velocities along 28 paths for Rayleigh waves and 17 paths for Love waves joining two stations with one from each cluster and using broadband records of earthquakes which lie nearly on the great circle joining the pair of stations. The phase velocities are in the period range of 10 to 275 s for Rayleigh waves and of 10 to 120 s for Love waves. The isotropic model obtained through inversion of the phase velocities indicates 199.1 km thick lithosphere with 3-layered crust of thickness 36.3 km; the top two layers have nearly same velocities and both constitute the upper crust with thickness of 12.6 km. The upper crust is mafic, whereas the lower crust is felsic. In the mantle lid, velocities increase with depth. The velocities of mantle lid beneath NW-IP is lower than those beneath south Indian Peninsula showing the former is hotter than the later perhaps due to large Phanerozoic impact on NW-IP. The significant upper mantle low velocity zone beneath NW-IP indicates high temperature which could be attributed to the past existence of a broad plume head at the west-central part of the Peninsula.</p>
Highlights
The Indian Peninsula is a combination of a few Precambrian cratonic nuclei and is one of the oldest Archean shield regions of the world
The south block consists of the north Dharwar craton, its northern part is covered by the Deccan trap flows and heart of the Deccan Volcanic Province (DVP), which is result of interaction between the mantle plume and the overriding continental lithosphere at ~65 Ma [White and Mckenzie 1989]
They showed Lithosphere-Asthenosphere boundary (LAB) depth is ~160 km in central India and increasing northward to ~250 km in the northern tip of the Indian Peninsula
Summary
The Indian Peninsula is a combination of a few Precambrian cratonic nuclei and is one of the oldest Archean shield regions of the world. Use of surface waves to find lithospheric velocity structure beneath Indian region has been reviewed by Bhattacharya [1992]. Such studies for 1D structure were based on analog data and generally of periods < 100 s. Further studies of upper mantle velocity structure beneath the Peninsular shield using long period surface waves are limited [Mitra et al 2006, Bhattacharya et al 2009]. The topology of LAB has been estimated by Priestley and Mckenzie [2006] by converting S-wave velocity (VS) into temperature profiles and fitting the geotherms beneath Eurasian plate They showed LAB depth is ~160 km in central India and increasing northward to ~250 km in the northern tip of the Indian Peninsula. The derived results are used to study (i) crustal structure (ii) nature of mantle lid and depth of LAB; and (iii) characteristics of upper mantle LVZ
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