Crustal Structure Beneath India and Tibet: New Constraints From Inversion of Receiver Functions

Abstract

The Indian subcontinent comprises geological terranes of varied age and structural character. In this study, we provide new constraints to existing crustal models by inverting the P‐to‐s receiver functions (RFs) at 317 broadband seismic stations. Inversion results fill crucial gaps in existing velocity models (CRUST1.0 and SEAPS) by capturing regions which are less represented. The final model produced is much more heterogeneous and is able to capture the structural variations between closely spaced seismic stations. In comparison to the global models, major differences are seen for seismic stations located over various rift zones (e.g., Godavari, Narmada, and Cambay) and those close to the coastal regions where transition from oceanic to continental crust is expected to create drastic changes in the crustal configuration. Seismic images are produced along various profiles using 49,682 individual RFs recorded at 442 seismic stations. Lateral variations captured using migrated images across the Himalayan collisional front revealed the hitherto elusive southern extent of the Moho and intracrustal features south of the Main Central Thrust (MCT). Poisson's ratio and crustal thickness estimates obtained using H‐k stacking technique and inversion of RFs are grossly similar lending credence to the robustness of inversions. An updated crustal thickness map produced using 1,525 individual data points from controlled source seismics and RFs reveals a (a) thickened crust (>55 km) at the boundary of Dharwar Craton and Southern Granulite Terrain, (b) clear difference in crustal thickness estimates between Eastern Dharwar Craton and Western Dharwar Craton, (c) thinner crust beneath Cambay Basin between southwest Deccan Volcanic Province and Delhi‐Aravalli Fold Belt, (d) thinner crust (<35 km) beneath Bengal Basin, (e) thicker crust (>40 km) beneath paleorift zones like Narmada Son Lineament and Godavari Graben, and (f) very thick crust beneath central Tibet (>65 km) with maximum lateral variations along the Himalayan collision front.

A review of seismological research in India during the past five years (2015-2019)

“…This was corroborated by the models obtained by inversion of P to s receiver functions at 317 broadband seismic stations covering entire India (Singh et al, 2016). The inversion results (Singh et al, 2017) greatly improved the existing global/regional velocity models (CRUST1.0 and SEAPS), primarily beneath various rift zones (e.g., Godavari, Narmada, and Cambay) and those close to the coastal regions where the transition from oceanic to continental crust is expected to cause drastic 532 G Srijayanthi et al changes in the crustal configuration. The rift zones of the Godavari and Narmada-Son Lineament show a thicker crust(>40 km) compared to the adjacent regions.…”

Moho Beneath Tibet Based on a Joint Analysis of Gravity and Seismic Data

“…Seismic methods were extensively used to determine the Moho topography beneath the Tibetan Plateau, primarily including seismic reflection (e.g., Gao et al, 2013;Lu et al, 2009;Zhang & Klemperer, 2005; see Zhang et al (2013), for a review), deep seismic sounding profiles (e.g., Teng et al, 2013Teng et al, , 2014Wang et al, 2017), receiver function analysis (e.g., Kind et al, 2002;Lou et al, 2009;Singh et al, 2017;Tian et al, 2014; see Li et al (2014) for a review), and seismic tomography (e.g., Koulakov et al, 2015;Obrebski et al, 2012). Recently, some regional models for the China mainland (Li et al, 2014), Asia and adjacent areas (Stolk et al, 2013), and the global models (e.g., Szwillus et al, 2019) have been compiled by interpolating the ©2020.…”

An Approach to Moho Topography Recovery Using the On-Orbit GOCE Gravity Gradients and Its Applications in Tibet

“…To validate the local recognition capability of our method, another model was employed from [59], which provides the discrete crustal thickness in India and Tibet with new constraints using the receiver functions. Crustal thickness is the sum of Moho depth below the sea level and the elevation above the sea level.…”

“…For comparison, the Moho depths from MJ and the CRUST 1.0 were transferred to crustal thickness by adding the elevations of surface provided by the CRUST 1.0. Figure 6 shows the crustal thickness from Singh et al (2017) [59], CRUST 1.0 and MJ. The receiver functions are Comparing Figures 4 and 5, the spatial patterns of Moho topography between our study and CRUST 1.0 are similar.…”

“…For comparison, the Moho depths from MJ and the CRUST 1.0 were transferred to crustal thickness by adding the elevations of surface provided by the CRUST 1.0. Figure 6 shows the crustal thickness from Singh et al (2017) [59], CRUST 1.0 and MJ. The receiver functions are regarded as the most powerful tool for revealing the crustal thickness, and the results from [59] are considered to be the most reliable model.…”