HR: 0830h
AN: S41A-08    [Abstracts]
TI: Crustal and Upper Mantle Structure Beneath the Western Ghats in the Deccan Volcanic Province
AU: * Tiwari, P K
EM: pankajtiwari@iitb.ac.in
AU: Surve, G
EM: ganpat@iitb.ac.in
AU: Gollapally, M
EM: gmohan@iitb.ac.in
AB: Receiver function studies were carried out to image the crustal and sub crustal structure beneath the Western ghats in the western segment of the Deccan Volcanic Province of India. About 500 teleseismic events recorded by a seismic network comprising of 5 stations including 2 broadband and 3 short period stations deployed in an area of 300 km2 in the Western ghats, about 200km NE of Mumbai were used. Strong P-to-s conversions are observed at all stations from the base of the Deccan Traps and the Moho. The crustal thickness in this region is observed to average 34km.The crustal composition as inferred from the Poisson's ratio of 0.26 is felsic to intermediate. A prominent feature observed in the RFs from the Broadband station is the pronounced negative peak at 6s immediately following the Pms conversion from the Moho. Absence of intracrustal layers suggests that this phase is not an artifact and possibly reflects a shallow sub-Moho LVL. Synthetics were generated to model the negative phase which revealed a 20km thick low velocity zone with 4-5 percent lower velocities in the shallow upper mantle beneath the Western ghats. A similar LVL is observed even in the coastal plains adjoining the Western ghats near Mumbai. The regional presence of the shallow sub-Moho LVL along the west coast suggests that it may represent signatures of rift related volcanism associated with the seperation of Seychelles from India.
DE: 7200 SEISMOLOGY
DE: 7205 Continental crust (1242)
DE: 7218 Lithosphere and upper mantle
DE: 8100 TECTONOPHYSICS
SC: Seismology [S]
MN: 2005 Joint Assembly