Ambient noise Love wave tomography in the eastern margin of the Tibetan plateau

We collected continuous waveform data from June to December 2007 recorded by 49 broadband seismic stations in western Sichuan and eastern Tibet, and applied an ambient noise technique to obtain a high-resolution tomography model of the crust beneath the eastern margin of the Tibetan plateau. Cross-correlations of ambient noise data are calculated in one-hour segments and stacked over 7 months. Then Love wave group dispersion curves along approximately 700-station pairs were determined using the multiple-filter analysis method. The study region was divided into a grid of 0.2° × 0.2°, and group velocity distribution maps between 8 and 40 s were obtained. The Love wave group velocity maps show good correlations with surface features. From the group velocity maps we inverted a 3-D model for SH wave velocity. The inferred SH velocity heterogeneities generally agree with variations in SV derived from Rayleigh wave dispersion, discrepancies between them are examined in view of non-uniqueness of the models and radial anisotropy. Both the Rayleigh and Love wave inversions show the significant difference of the crustal structure and reveal a prominent low-velocity zone within the mid-to-lower crust beneath the eastern margin of the Tibetan plateau.