Shear Wave Velocity Structure beneath Maitri station in Dronning Maud Land, East Antarctica from Joint Inversions of Rayleigh Wave Ellipticity, Multimode Surface Waves and Diffused Wave Horizontal-to-Vertical Spectral Ratios

Dronning Maud Land (DML) in East Antarctica, a stable cratonic block, is explored to understand the evolution of the Gondwana supercontinent. This study investigates the capabilities of the Rayleigh Wave Ellipticity (RWE) and the horizontal-to-vertical spectral ratio (HVSR), assuming equipartitioned phases or diffused field assumption (DFA) of ambient noise field (ANF), to assess shallow crustal shear velocity. Using data from India's permanent broadband seismic station at Maitri (MAI) in DML, we analyse the crustal and shallow shear velocity in the frequency range 0.02 Hz (50 s period) to 10 Hz (0.1 s period) from 2013 to 2017, excluding disturbance periods. The RWE is extracted with two different methods, and the geometric mean of RWE and HVSR is compared. Both RWE and HVSR curves show a stable shape with a low-frequency peak around ∼0.03 Hz, indicating a deep velocity contrast. A peak near ∼6 Hz is observed but with wide variations and smaller peak amplitudes, possibly due to ice thickness or permafrost variations. Using a reference shear velocity model from a previous receiver function (RF) study at MAI, we apply non-linear inversions on RWE and HVSR (DFA) curves for crustal velocity profiles up to ∼50 km. Joint inversions with multimodal surface-wave dispersion curves minimize inversion non-uniqueness, yielding a good match with RF model. The derived shear velocity models show a distinct velocity contrast at 30–35 km depth (possibly the Moho) and a shallow, low-velocity sedimentary layer at 150–800 m depth, with a possible high-velocity, densified layer at ∼3 km depth.