Crustal Seismic Structure in Jammu and Kashmir Region, India

A seismic line was recorded in the Jammu-Kashmir region, during the year 1978, as part of the International Pamir-Himalayan project. The data available on this line are in analog form. The first arrival refraction data in most cases appears to be reliable but only a few later arrival reflection events can be identified from four shot points. The recording is in two segments, Naoshera-Thannamandi in the Jammu region and Babarishi-Muquam in the Kashmir region. First results on the studies along this profile were published by Kaila et al. (1984). In the present interpretation, the first arrival data from the above segments were used to delineate the sedimentary basin configuration and the wide angle data to prepare a crustal model. The data were analyzed by ray inversion technique. The depth section on the Naoshera - Thannamandi segment shows a four-layered sedimentary layer configuration with velocities of 1.9, 4.1, 4.4-5.3 and 5.9-6.1 kms^-l, the deepest layer being at about 4.7 km depth between Naoshera and the Main Boundary Thrust (MBT). To the north of the MBT the deepest layer is at a depth of -2.0 km. The 5.9-6.1 kms^-l velocity does not seem to represent the basement of the sedimentary column, which according to hydrocarbon related geophysical and drilling results is expected at a depth exceeding 8 km in the Jammu region. The Babarishi-Maquam section shows a three-layered structure with velocities of 1.7-2.1,4.0 and 5.5-6.0 kms^-l. The 5.5-6.0 kms^-lvelocity is likely to represent the Panjal Traps, which form the basement for the sedimentary cover. A patchy reflection at 6.0 tolO.0 km depth in the Jarnmu region and -8.0-10.5 km depth in the Kashmir region may represent either the Precambrian or exhumed lower crustal rocks as basement, The crustal velocity model shows a layer of velocity 6.8 kms^-l at -36.0 km depth and Moho with an inferred boundary velocity of 8.2 kms^-l, at 40.0 - 43.0 km depth in the central part of the profile. The gravity model indicates that the Moho is deepening from -38 km at Naoshera to -48 km at Muquarn.