HR: 1340h
AN: S53B-0219    [Abstracts]
TI: Moho Configuration from a Single Fold Reflection Profile obtained from a Seismic Refraction Survey in the Deccan Trap Region, India
AU: * Rao, K
EM: koteswara999@rediffmail.com
AF: National Geophysical Research Institute, Hyderabad, Hyderabad, AP 500 007 India
AU: Raju, S
AF: National Geophysical Research Institute, Hyderabad, Hyderabad, AP 500 007 India
AU: Kumar, M R
AF: National Geophysical Research Institute, Hyderabad, Hyderabad, AP 500 007 India
AU: Sarkar, D
AF: National Geophysical Research Institute, Hyderabad, Hyderabad, AP 500 007 India
AU: Reddy, P R
AF: National Geophysical Research Institute, Hyderabad, Hyderabad, AP 500 007 India
AU: Brown, L D
EM: brown@geology.cornell.edu
AF: Institute for the Study of the Continents, Cornell University, Ithaca, NY 14853 United States
AB: Controlled Source Seismic (CSS) studies by the National Geophysical Research Institute (NGRI) were carried out during 2001 - 03 along nine select traverses (E-W and N-S) in the Narmada and Tapti river basin, India. A total of 705 km of refraction data, with record lengths of 20 seconds, were collected using a 120 channel Radio Frequency Telemetry (RFT) system (EAGLE 88) in SEG-D format. A 40 km long line from Jhagadia to Rajpipla (W-E direction) is here interpreted on the basis of both refracted and reflected phases. Processing of the first 6-8 sec focused on the basement configuration. Conventional ray tracing analysis of refracted and wide angle reflected phases constrains the velocity structure to about 10 km depth: from surface to depth the key units include a Recent formation with velocity of 1.9 to 2.3 km/s, a Quaternary unit with a velocity 2.9 - 3.3 km/s, traps with velocity varying from 4.8 to 5.2 km/s, low velocity Mesozoic sedimentary rocks with a velocity of 4.3 km/s, all underlain by granitic basement with velocity varying between 5.8 and 6.1 km/s. To investigate the lower crust the refraction data were reprocessed as a single fold seismic reflection profile extending to 20s travel time. Both mid-crustal and Moho reflections can be clearly identified. The Moho dips from east to west, with the Moho at a depth of 34 km below Jhagadia. The Moho depths, as well as the velocity structure derived from the reflection data, correlate well with the results from the Mehmadabad-Billimora 260 km long (N-S) deep seismic sounding profile (Kaila et al., 1981). This study demonstrates how reflection techniques can be used to extract additional information from previous refraction surveys in others parts of India.
DE: 9320 Asia
DE: 7294 Instruments and techniques
DE: 7205 Continental crust (1242)
SC: Seismology [S]
MN: 2004 AGU Fall Meeting