Possible depth and source localization of seismic anisotropy beneath Shillong Plateau and Himalayan foredeep region: An implication towards deformation mechanisms

Abstract

Estimation of source localization and central depth of anisotropy beneath an active seismic region plays an important role in understanding the deformation mechanism and current configuration of tectonics. Though shear wave splitting measurements are capable of deciphering the mantle dynamics and deformation patterns, they are constrained from analysing the actual depth of anisotropy or heterogeneity, which may have large influences in interpreting the geodynamics of a particular region. The present study fills this gap of estimating the source localization and depth of seismic anisotropy beneath the Shillong Plateau and Himalayan foredeep region through a well‐established spatial coherency analysis of splitting parameters based upon the Fresnel zone concept. The model suggests a central depth of heterogeneity at around 100 km beneath the Shillong Plateau mass, coinciding with the lithosphere‐asthenosphere boundary and strengthens our implication that the asthenospheric drag at the base of the Indian lithosphere is responsible for absolute plate motion of India, is the major source of anisotropy and controls the deformation patterns of the Shillong mass. In a similar manner, the spatial coherency analysis predicts a central depth of anisotropy at around 150 km beneath the Himalayan foredeep region. The asthenospheric force corresponding to this particular depth is suggested as the major source of anisotropy for this region.