The mapping of shallow upper mantle discontinuities using teleseismic P-wave autocorrelation

Crust and upper mantle discontinuities play a key role in understanding continental formation and evolution. The most prevalent seismic techniques, like receiver function, surface wave tomography, etc., face problems of multiples from shallow crustal discontinuities and low vertical resolution, respectively, which makes it difficult to image deeper discontinuities. To get the better of these complications and image the deeper discontinuities with greater accuracy, the P-wave autocorrelation method has been used for the teleseismic data recorded at Hyderabad station (HYB) in south India. This method has efficiently identified the major shallow upper mantle discontinuities down to 250 km depth. The Moho, mid-lithospheric discontinuity, Hales discontinuity, lithosphere-asthenosphere boundary and Lehmann discontinuity were observed at 30.37, 92.17, 123.43, 140.50 and similar to 201 km, respectively. We also achieved a very high vertical resolution (<0.6 km) for all the shallow upper mantle discontinuities. Further, we also proposed an iterative method to calculate the v(p)/v(s) ratio of the crust, using the arrival times of Moho reflected 2p and p + s phase. Unlike other seismic methods, this iterative method is independent of any constraint on v(p) and v(s). The v(p)/v(s) is found to be 1.744, suggesting the crust beneath HYB is felsic in nature.