CRUSTAL STRUCTURE AND MOHO TOPOGRAPHIC VARIATION OF BANGLADESH USING THE JOINT CCP (COMMON CONVERSION POINT) STACKING AND H-Κ ANALYSIS: AN APPROACH FROM RECEIVER FUNCTION TECHNIQUE

Variations of the crustal structure and moho topography beneath the Ganges-Brahmaputra delta has always been a point of interest to scientist because of the thick sediment cover above the basement complex. An attempt has been taken to improve the understanding of the crustal structure and moho topographic variation from the teleseismic events by employing the techniques of receiver function analysis. A large set of waveforms and traces of teleseismic earthquakes recorded between 2007-2020 from selective stations were retrieved using adequate pre-requisition processes. An iterative time-domain deconvolution approach was used for source normalizing based on the method of Ligorría & Ammon (1999). Necessary corrections, filters, PRF to depth migration, and velocity model of Kennett et al. (1995) were used throughout the computation during the basic stacking, CCP stacking and H-κ stacking. From the limited interpolation point, the CCP imaging reveals that the Moho depth possibly ranged between 30-35 km for the maximum stations. However, the H-κ analysis specifically inferred the Moho depth, Vp/Vs, and Poisson’s ratio for each station separately where RF amplitude from the moveout and BAZ section, the Ps arrival time between ~4.0s-6.0s, and Moho depth at ~30-35 km was found for the majorities. The systematic variations in the Moho Ps arrival and reverberations (PpPs, PsPs + PpSs) are well aligned with the findings of Singh et al. (2016) where the shallower Moho has been proposed. Moho depth beneath Shillong Plateau (32.5 km) is in good alignment with the results of Singh et al. (2016) and Mitra et al., (2005). The MPUR station showed interesting results where both Singh et al. (2016) and Mitra et al. (2018) agreed but we found a relatively lesser value. We also deduced that the MANK station is a good agreement with Mitra et al. (2018). Overall, our derived results can be used for a comparable argument with the findings of Singh et al. (2016) and Mitra et al. (2005, 2008, 2018) together. The moveout and backazimuth image sections will be very pivotal for future crustal studies, tectonics, and regional basin analysis for future resource development and earthquake hazard assessment.