Love-wave Group-Velocity Tomography of India-Tibet: Insights into Radially-Anisotropic S-Wave Velocity Structure

Ghosh, Manumoy (2025) Love-wave Group-Velocity Tomography of India-Tibet: Insights into Radially-Anisotropic S-Wave Velocity Structure. PhD thesis, Indian Institute of Science Education and Research Kolkata.

Text (PhD thesis of Monumoy Ghosh (16RS061)) 16RS061.pdf - Submitted Version Restricted to Repository staff only Download (26MB)

Abstract

Love (LQ) and Rayleigh-wave (LR) dispersion data provide essential constraints on radiallyanisotropic shear-wave velocity structure. SV models of India-Tibet are available from modeling of LR dispersion data, but reliable LQ dispersion measurements are limited. This is due to poor signal-to-noise (SNR) ratio on horizontal component waveforms, off great-circle-arc propagation and overtone interference. We overcome these limitations by performing systematic SNR test, polarization analysis and elimination of overtone interference, to compute fundamental-mode LQ group-velocity dispersion and tomography across India, Himalaya and Tibet, for period range of 10-120 s. Fundamental-mode group-velocity dispersion, in this period range, is sensitive to the crust and upper-mantle structure. Lateral resolution of the group-velocity maps vary from 4° (10-40 s) to 9°(90-120 s). Groupvelocities (absolute and anomaly) and its lateral variations match the regional-scale geologic and tectonic features. Up to 20 s period low-velocity sedimentary layers are observed in the Bengal and Indus Delta-Fan complexes, Himalaya and Suleiman Mountain foreland basins, Qaidam, Tarim and Eastern Tajik Basins. The Indian Cratons have higher group-velocities compared to the thickened Tibetan Plateau crust across the entire range of periods. At lower periods the western Tibetan Plateau is underlain by high-velocity anomaly and the east-central plateau has a broad zone of low-velocity anomaly. Finally, to test the nullhypothesis of isotropy, we use isotropic SV models to predict the observed LQ dispersion data. Our test negates the null hypothesis and suggest radially-anisotropic structure at least for the shallow-crust and upper-mantle beneath India-Tibet.

Actions (login required)

View Item