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Influence of Deccan volcanism/synrift magmatism on the crust–mantle structure and its implications for the seismogenesis of earthquakes occurring in the Kachchh rift zone

By
Prantik Mandal
Prantik Mandal
CSIR-NGRI, Hyderabad-500007, India
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Published:
January 01, 2017

Abstract

The present study focuses on the delineation of the crust–mantle structure underlying the Kachchh rift zone (KRZ), by modelling P-wave receiver functions (P-RFs) and P-wave teleseismic tomography. Our RF study delineates marked crustal and lithospheric thinning below the central KRZ relative to the unrifted surrounding regions. This thinning model receives further support from crust-corrected normalized P-residuals, which suggest dominant negative residuals associated with the central KRZ. Teleseismic tomography using these P-residuals reveals low velocity to a depth of 170 km below the central KRZ, while there are positive residuals associated with the surrounding unrifted zones. Such a complex heterogeneous crust–mantle structure, which could be related to K/T boundary Deccan mantle plume activity and rift-related magmatism, might play a crucial role in seismogenesis of lower crustal earthquakes that have occurred in the KRZ since 2001. Inverted crust–mantle models obtained from P-RFs suggest a low shear velocity zone extending from 70–110 to 170–220 km depth beneath the central KRZ. This receives further support from the presence of low P-wave velocity down to 170 km modelled using teleseismic tomography. This low V p and V s zone in the upper mantle could be explained by the presence of trapped melts related to Deccan volcanism at 65 Ma or older rift-related magmatism.

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Geological Society, London, Special Publications

Tectonics of the Deccan Large Igneous Province

S. Mukherjee
S. Mukherjee
Department of Earth Sciences, Indian Institute of Technology Bombay, Mumbai 400 076, Maharashtra, India
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A. A. Misra
A. A. Misra
Exploration, Reliance Industries Ltd, Mumbai 400 701, Maharashtra, India
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G. Calvès
G. Calvès
Université Toulouse 3, Paul Sabatier, Géosciences Environnement Toulouse, 14 avenue Edouard Belin, 31400, Toulouse, France
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M. Nemčok
M. Nemčok
EGI at University of Utah, 423 Wakara Way, Suite 300, Salt Lake City, UT 84108, USAEGI Laboratory at SAV, Dúbravskácesta 9, 840 05 Bratislava, Slovakia
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Geological Society of London
Volume
445
ISBN electronic:
9781786203281
Publication date:
January 01, 2017

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