INDOVSV24: A 3D shear wave velocity model of the Lithosphere-Asthenosphere system beneath the Indian Ocean

The structure of the lithosphere-asthenosphere system beneath the Indian Ocean remains one of the most enigmatic and relatively understudied among the world's ocean basins, mainly because of its complex geological settings and diverse seismotectonic features. Therefore, the present study aims to delineate the shear‐wave velocity structure of the Lithosphere–Asthenosphere System beneath the Indian Ocean using surface wave tomography. For this analysis, we considered waveforms from events sampling the study region with a magnitude ≥ 5.0, recorded at 856 selected seismic stations operated under 44 seismic networks, with epicentral distances between 20° and 100°. To ensure high data quality, only waveforms with a signal-to-noise ratio (SNR) ≥ 2.5 were retained. Dispersion analysis was then performed on the pre-processed data to manually pick the dispersion curves. This procedure resulted in ~32,000 Rayleigh-wave dispersion curves, with periods ranging from 18 to 180 s. These high-quality dispersion measurements were used to derive regionalized Rayleigh‐wave group velocities, which were subsequently inverted using a trans-dimensional approach to obtain the shear wave velocities. The resulting 3D shear velocity model, INDOV_SV24, provides an improved lateral resolution of 200 to 600 km down to depths of 300 km, significantly enhancing the resolution compared with previous studies. This model shows excellent correlation with surface tectonics and accurately delineates significant features such as mid-oceanic ridges and subduction zones. Intriguingly, our model and tectonic regionalization results identify a distinct low-velocity anomaly oriented in the SW-NE direction with a localized strong low-velocity anomaly/reservoir in the north-eastern side within the Indo-Australian Diffusion Plate Boundary (IADPB) zone. This observation aligns with seafloor age data, indicating a relatively younger age (~40 Ma) in this region compared to its surrounding areas. The strong low-velocity anomaly/reservoir (DPB_LVZ) within the IADPB zone on the western side of the Sunda subduction zone (SSZ) may result from the accumulation of asthenosphere material from the ridges near the sub-slab side of the subducting Sunda plate, along with upwellings facilitated from deeper sources. These seismological findings strongly suggest ongoing active dynamics in the Indo-Australian Diffusion Plate Boundary Zone.