Mantle Flow and Fault Zone Related Seismic Anisotropy Revealed in Sri Lanka: Evidence from Shear Wave Splitting
Year: 2025
Type: preprint
Abstract: Sri Lanka occupies a key position in the reconstruction of Eastern Gonwanaland to its present connection with the Indian Subcontinent. Although existing discussions on upper mantle anisotropy beneath Sri Lanka have continued, direct observational evidence has been limited. In this study, we analyzed seismic anisotropy in the upper mantle beneath Sri Lanka using 280 teleseismic S and SKS waveform observations recorded at IRIS and GEOFON broadband seismic stations located across three prominent tectonic units. Forward modeling of the dependence of the splitting parameters on incoming polarization, assuming a horizontal axis of symmetry, brings out two layers of anisotropy beneath Sri Lanka, with fast axis azimuths oriented N15°E in the lower layer and N58.3°E in the upper layer. While stronger anisotropy (δt ≈ 1 s) in the lower layer is related to mantle flow, a weaker one (δt ≈ 0.3 s) in the upper layer could represent preexisting anisotropy in the fault zone. Comparisons with absolute plate motion models suggest that the motion of the Indian plate aligns with the fast directions observed in the lower layer, and upper layer attributes to protracted episodes of deformation. These findings provide critical constraints for understanding the regional tectonic context and the dynamics of the upper mantle beneath Sri Lanka.
Language: English
Subfield: Geophysics
Field: Earth and Planetary Sciences
Domain: Physical Sciences
Open Access status: gold
Award: G5464929342
OpenAlex ID: W4414602437
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