2-D Crustal Velocity Structure Along Hirapur-Mandla Profile in Central India: An Update

Abstract

The 2-D crustal velocity model along the Hirapur-Mandla DSS profile across the Narmada-Son lineament in central India (MURTY et al., 1998) has been updated based on the analysis of some short and discontinuous seismic wide-angle reflection phases. Three layers, with seismic velocities of 6.5-6.7, 6.35-6.40 and 6.8 km s )1 , and upper boundaries located approximately at 8, 17 and 22 km depth respectively, have been identified between the basement (velocity 5.9 km s )1 ) and the uppermost mantle (velocity 7.8 km s )1 ). The layer with 6.5-6.7 km s )1 velocity is thin and is less than 2-km deep between the Narmada north (at Katangi) and south (at Jabalpur) faults. The upper crust shows a horst feature between these faults, which indicates that the Narmada zone acts as a ridge between two pockets of mafic intrusion in the upper crust. The Moho boundary, at 40-44 km depth and the intra-crustal layers exhibit an upwarp suggesting that the Narmada faults have deep origins, involving deep-seated tectonics. A smaller intrusive thickness between the Narmada faults, as compared to those beyond these faults, suggests that the intrusive activities on the two sides are independent. This further suggests that the two Narmada faults may have been active at different geological times. The seismic model is constrained by 2-D gravity modeling. The gravity highs on either side of the Narmada zone are due to the effect of the high velocity/high density mafic intrusion at upper crustal level.

Optimal Design of a Gravity Survey Network and its Application to Delineate the Jabera-Damoh Structure in the Vindhyan Basin, Central India

“…It is also seen in the model that the granite layer is missing in the right margin of the faulted basin whereas it has a thin patch in its left side of the faulted segment. This conforms to the reported DSS modeling (MURTY et al, 2004).…”

“…Using constraints from the borehole data (DAS et al, 1999) and DSS studies (MURTY et al, 2004) Vol. 164, 2007 Optimum Design of Survey Network 2019 scaling spectral analysis (MAUS and DIMRI, 1994, 1995a,b, 1996 of the data.…”

Subcrustal Low Velocity Layers in Central India and their Implications

“…2414 A. S. N. Murty et al Pure appl. geophys., correlatable crustal P-wave phases P 3 P to P M P (MURTY et al, 2004), in the record section of SP 235, the presence of prominent reflection phases P 6 P-P 9 P (Fig. 2a).…”

“…Observed record section (normalized) of SP 235 recorded towards SP 0 (distances are from SP 0) along the profile assembled from the digitized data of DSS records (trace interval 800 m). Theoretical travel-time curves, corresponding to the velocity-depth model of MURTY et al (2004) are shown as (P 3 P to P M P) for various phases correlated in the record section. P 6 P, P 7 P, P 8 P and P 9 P are the subcrustal reflection phases identified and modeled in the present study.…”

“…1) to derive a kinematically and dynamically wellconstrained subcrustal velocity structure by travel time and amplitude analysis. Recent modeling studies (MURTY et al, 1998(MURTY et al, , 2004 provide the crustal velocity control (Figure 4(c), crustal velocity model) to the present subcrustal studies.…”